Leeway shown by account in theatre poster (8)
I believe the answer is:
playbill
'theatre poster' is the definition.
(I've seen this before)
'leeway shown by account' is the wordplay.
'leeway' becomes 'play' (I've seen this in another clue).
'shown by' is a charade indicator (letters next to each other).
'account' becomes 'bill' (synonyms).
'play'+'bill'='PLAYBILL'
'in' is the link.
(Other definitions for playbill that I've seen before include "Theatrical poster" , "Theatre poster" , "advertisement for drama" .)