Swear numbhead put out reply (6)
I believe the answer is:
answer
'reply' is the definition.
(synonyms)
'swear numbhead put out' is the wordplay.
'numbhead' becomes 'n' (head letter of 'numb').
'put out' indicates anagramming the letters.
'swear'+'n'='swearn'
'swearn' with letters rearranged gives 'ANSWER'.
(Other definitions for answer that I've seen before include "Reply or solution" , "Be satisfactory" , "Write back" , "Solve - solution" , "It could give you a" .)