Puts nuts outside back of cage, creating agitation (5)
I believe the answer is:
upset
'agitation' is the definition.
(upset is a kind of agitation)
'puts nuts outside back of cage' is the wordplay.
'nuts' indicates an anagram (nuts can mean crazy).
'outside' is an insertion indicator.
'back of' suggests the final letters.
The final letter of 'cage' is 'e'.
'puts' with letters rearranged gives 'upst'.
'upst' placed around 'e' is 'UPSET'.
'creating' acts as a link.
(Other definitions for upset that I've seen before include "Overturn, tip over" , "turned over" , "Complaint" , "overcome" , "Discomfit" .)