Signed to get the gun back: badly needs to carry it (8)
I believe the answer is:
endorsed
'signed' is the definition.
(endorsing is a kind of signing)
'badly needs to carry it' is the wordplay.
'badly' indicates anagramming the letters.
'to carry' is an insertion indicator.
'it' becomes 'dor' (I am not sure about this - if you are sure you should believe this answer much more).
'needs' with letters rearranged gives 'ensed'.
'ensed' going around 'dor' is 'ENDORSED'.
'to get the gun back' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for endorsed that I've seen before include "Given public approval" , "Signed one's name to certify" , "Seconded" , "Officially approved" , "Certified or supported" .)