Camera captures poor Mame in US prison (7)
I believe the answer is:
slammer
'us prison' is the definition.
(US slang for prison)
'camera captures poor mame' is the wordplay.
'camera' becomes 'SLR' (single-lens reflex camera).
'captures' indicates putting letters inside.
'poor' indicates anagramming the letters.
'mame' anagrammed gives 'amme'.
'slr' placed around 'amme' is 'SLAMMER'.
'in' is the link.
(Other definitions for slammer that I've seen before include "one leaping into crowd" , "Pickwickian doctor" , "He noisily leaves the room" , "Prison (colloq.)" , "One pulling off lots of tricks" .)