Garden confines male prisoner (7)
I believe the answer is:
hostage
'prisoner' is the definition.
(hostage is a kind of prisoner)
'garden confines male' is the wordplay.
'garden' becomes 'hoe' (to garden could mean to hoe).
'confines' indicates putting letters inside.
'male' becomes 'stag' (a stag is a male deer).
'hoe' enclosing 'stag' is 'HOSTAGE'.
(Other definitions for hostage that I've seen before include "Person held by kidnapper for ransom" , "person captive to fortune" , "Person taken as security" , "She-goat (anag)" , "Prisoner kept as security" .)