British soldier back in prison (4)
I believe the answer is:
brig
'prison' is the definition.
(thesaurus)
'british soldier back' is the wordplay.
'british' becomes 'br'.
'soldier' becomes 'gi' (government issue or general issue**).
'back' shows that the letters should be reversed in order.
'gi' backwards is 'ig'.
'br'+'ig'='BRIG'
'in' acts as a link.
(Other definitions for brig that I've seen before include "A ship; army officer (abbr.)" , "Ship; a ship's jail" , "Two-masted square-rigged sailing ship" , "'Two-masted,square-rigged ship (4)'" , "Two-masted ship; gaol" .)