Break code -- task providing defence (8)
I believe the answer is:
stockade
'defence' is the definition.
(stockade is a kind of defence)
'break code task' is the wordplay.
'break' is an anagram indicator.
'code'+'task'='codetask'
'codetask' is an anagram of 'STOCKADE'.
'providing' is the link.
(Other definitions for stockade that I've seen before include "military prison" , "Cod steak consumed in enclosure as for military prisoners" , "defensive structure" , "Fortified enclosure" , "Defensive enclosure built of tall heavy posts" .)