Small company representative has to play a part (7)
I believe the answer is:
compact
'small' is the definition.
(I've seen this before)
'company representative has to play a part' is the wordplay.
'company' becomes 'co' (abbreviation).
'representative' becomes 'mp'.
'has' means one lot of letters go next to another.
'to play a part' becomes 'act' (I've seen this before).
'co'+'mp'+'act'='COMPACT'
(Other definitions for compact that I've seen before include "Dense; powder case" , "Small case for face powder" , "The powder-box is closely packed" , "Close - agreement - make-up case" , "woman's case" .)