SLORMGORM kicks off the week…
A thoroughly enjoyable puzzle with some lovely surfaces, as one expects from this setter. I'm not quite sure about my parsing of 20a… maybe there's something else going on.
Thanks SLORMGORM!

ACROSS
1. Reported description of Trotsky’s assassin? (8)
MARKSMAN
"Marx man" = MARKSMAN (description of Trotsky, "reported")
5. Professional able to make an excess of revenue (6)
PROFIT
PRO (professional) + FIT (able)
10. Ancestry series gets silver medal (that’s only 2nd place!) (7)
LINEAGE
LINE (series) gets AG (silver) + [m]E[dal] (that's only 2nd place)
11. Guy going about island without bit of sleep is a state (7)
NAMIBIA
(MAN)< (guy, <going about) + IBI[z]A (island, without Z (bit of sleep))
12. Broadcaster in streetcar travelling around (9)
SCATTERER
(STREETCAR)* (*travelling around)
13. I’m alarmed if president punches Yankee and son (5)
YIKES
IKE (president) punches (Y (Yankee) and S (son))
15. One downed wine that’s brought over (5)
EIDER
(RED (wine) + IE (that's))< (<brought around)
16. Jet or blue ribbed fabric on back of costume (8)
CONCORDE
CON (blue) + CORD (ribbed fabric) on [costum]E (back of)
19. A pen that might be seen around a cob? (8)
BIRDCAGE
20. City stars needing to make a break in the centre (5)
LEEDS
LEADS (stars, needing to make a break in the centre)
21. Dope smuggled by a model-type and actor (5)
AGENT
GEN (dope) smuggled by (A + T (model-type))
23. PDC primarily broadcast a set shot at the double (9)
POSTHASTE
P[dc] (primarily) + (A SET SHOT)* (*broadcast)
25. One installing Windows in Gulf’s more idle (7)
GLAZIER
G (Gulf) + LAZIER (more idle)
27. Company by motorway stronghold gets relief (7)
COMFORT
CO (company) by M (motorway) + FORT (stronghold)
28. Property in Spain controlled by the government (6)
ESTATE
E (Spain) + STATE (controlled by the government)
29. Those in van in repose must be whacked (8)
PIONEERS
(IN REPOSE)* (*must be whacked)
DOWN
1. Sweetly thick sort of male seen with old girls (8)
MOLASSES
M (male) seen with O (old) + LASSES (girls)
2. Ordinary men can be offensive as well as row (4,3,4)
RANK AND FILE
RANK (offensive) + AND (as well as) + FILE (row)
3. Tired and in bits? (9)
SHATTERED
4. A fellow extremely angry right-wing leaders frighten (5)
AFEAR
A F[ellow] E[xtremely] A[ngry] R[ight-wing] (leaders)
6. Game of cards is rotten when you have no clubs (5)
RUMMY
[c]RUMMY (rotten, when you have no C (clubs))
7. Porky female seen with one heading for bakery (3)
FIB
F (female) seen with I (one) + B[akery] (heading for)
8. Vehicles with on-board computers rolled over (5)
TRAMS
(SMART)< (with on-board computers, <rolled over)
9. Where one might see Edinburgh comic break? (8)
INFRINGE
IN FRINGE (where one might see Edinburgh comic)
14. Cause of complaint doctor in Keys noted (6,5)
KIDNEY STONE
(IN KEYS NOTED)* (*doctor)
16. Bubbly title-holders embracing old head of state (8)
CHAMPERS
CHAMPS (title-holders) embracing ER (old head of state)
17. American monk with a halo in need of adjustment (9)
OKLAHOMAN
(MONK with A HALO)* (*in need of adjustment)
18. Awful boss eats stuff that is bad for you (8)
ASBESTOS
21. Fish hang loosely after end of rod is removed (5)
ANGLE
[d]ANGLE (hang loosely, after [ro]D (end of) is removed)
22. Tense, good man taking off close to rivers could be Sully (5)
TAINT
T (tense) + [s]AINT (good man, taking off [river]S (close to))
24. Some mafioso chilling in a Russian city (5)
SOCHI
[mafio]SO CHI[lling] (some)
26. Craft seen by planet without wings (3)
ART
[e]ART[h] (planet, without wings)
Yes, LEEDS is LEADS making (the) A an E (brEak in the centre).
Tired/shattered? Con/blue? Please explain.
Thanks Slormgorm and Teacow
16ac: blue n 5 Brit an informal name for Tory (Collins 2023 p 224); and then Tory 1 a member or supporter of the Conservative Party in Great Britain or Canada (p 2084).
3dn: shattered adj 4 informal tired out or exhausted (Collins 2023 p 1828).
I see. Thank you, Pelham. I couldn’t find them in Collins online.
A satisfying Monday puzzle. SOCHI my favourite with an aptly amusing surface in more ways than one.
Thanks Slormgorm (especially for parsing NAMIBIA) and Teacow.
Another good ‘un after Saturday’s strong outing. Liked Marksman, Eider, birdcage, asbestos.