Shabby trio framing poster, say, at pub (10)
I believe the answer is:
threadbare
'shabby' is the definition.
(I've seen this before)
'trio framing poster say at pub' is the wordplay.
'trio' becomes 'three' (synonyms).
'framing' means one lot of letters goes inside another (inserted letters are framed by the outside letters).
'poster say' becomes 'ad' (a poster might be an advertisement).
'at' is a charade indicator (letters next to each other).
'pub' becomes 'bar' (both are drinking establishments).
'ad'+'bar'='adbar'
'three' placed around 'adbar' is 'THREADBARE'.
(Other definitions for threadbare that I've seen before include "poor" , "deprived of nap" , "Tired" , "Shabby" , "Well-worn" .)