Hold criminal - one in brown (7)
I believe the answer is:
contain
'hold' is the definition.
('contain' can be a synonym of 'hold')
'criminal one in brown' is the wordplay.
'criminal' becomes 'con' (abbreviation for 'convict').
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'brown' becomes 'tan' (tan is a kind of brown).
'i' put inside 'tan' is 'tain'.
'con'+'tain'='CONTAIN'
(Other definitions for contain that I've seen before include "Control, restrain" , "I cannot (anag) - hold back" , "Include - restrict" , "Keep the lid on" , "Accommodate" .)