Pictures soldiers put up swiped by American investigators (6)
I believe the answer is:
cinema
'pictures' is the definition.
(I've seen this before)
'soldiers put up swiped by american investigators' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'put up' shows that the letters should be reversed in order.
'swiped by' means one lot of letters goes inside another.
'american investigators' becomes 'cia' (I can't explain this - if you can you should believe this answer much more).
'men' reversed gives 'nem'.
'nem' placed inside 'cia' is 'CINEMA'.
Can you help me to learn more?
(Other definitions for cinema that I've seen before include "Where films are shown" , "Modern art" , "Movie-house" , "(Building for) film" , "Local form of language" .)