Chaps turning up in American agency for pictures (6)
I believe the answer is:
cinema
'for pictures' is the definition.
(I've seen this in another clue)
'chaps turning up in american agency' is the wordplay.
'chaps' becomes 'men' (chap can mean a man).
'turning up' shows that the letters should be reversed in order.
'in' is an insertion indicator.
'american agency' becomes 'CIA' (Central Intelligence Agency).
'men' backwards is 'nem'.
'nem' going within 'cia' is 'CINEMA'.
(Other definitions for cinema that I've seen before include "Odeon perhaps" , "(Building showing) films" , "Iceman (anag)" , "Film industry" , "place for pictures" .)