Reluctance to proceed: code left to be cracked (4,4)
I believe the answer is:
cold feet
'reluctance to proceed' is the definition.
(having cold feet means being reluctant)
'code left to be cracked' is the wordplay.
'to be cracked' indicates anagramming the letters.
'code'+'left'='codeleft'
'codeleft' anagrammed gives 'COLD FEET'.
(Other definitions for cold feet that I've seen before include "result of paddling in winter ?" , "Icy extremities for slang fear" , "You'd have them if you were afraid to proceed" , "Apprehension" , "You might have them if you're afraid to proceed" .)