Underwear market surrounded by paramilitary force (6)
I believe the answer is:
smalls
'underwear' is the definition.
(I've seen this before)
'market surrounded by paramilitary force' is the wordplay.
'market' becomes 'mall' (shopping mall).
'surrounded by' indicates putting letters inside.
'paramilitary force' becomes 'ss'.
'mall' inserted into 'ss' is 'SMALLS'.
(Other definitions for smalls that I've seen before include "Underwear (colloq.)" , "Slips perhaps" , "Undersized underwear?" , "Underclothes" , "Diminutive items of underwear" .)