Pickpocket maybe one the force imprisons (5)
I believe the answer is:
thief
'pickpocket' is the definition.
(I've seen this before)
'one the force imprisons' is the wordplay.
'one' becomes 'i' (Roman numeral).
'force' becomes 'f' (symbol used in Physics e.g. f=ma).
'imprisons' is an insertion indicator.
'the'+'f'='thef'
'i' inserted within 'thef' is 'THIEF'.
'maybe' is the link.
(Other definitions for thief that I've seen before include "Stealer" , "See 3" , "Crook" , "'Taffy was a - - '" , "Person who steals things" .)