Chaps turning up in American agency for pictures (6)
I believe the answer is:
cinema
'for pictures' is the definition.
(I've seen this before)
'chaps turning up in american agency' is the wordplay.
'chaps' becomes 'men' (chap means a man).
'turning up' says the letters should be written backwards.
'in' means one lot of letters goes inside another.
'american agency' becomes 'CIA' (Central Intelligence Agency).
'men' written backwards gives 'nem'.
'nem' placed into '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" .)