Finish off a linen hat I fashioned (10)
I believe the answer is:
annihilate
'finish off' is the definition.
(thesaurus)
'a linen hat i fashioned' is the wordplay.
'fashioned' indicates anagramming the letters.
'linen'+'hat'+'i'='linenhati'
'linenhati' with letters rearranged gives 'nnihilate'.
'a'+'nnihilate'='ANNIHILATE'
(Other definitions for annihilate that I've seen before include "Completely defeat" , "Wipe out" , "Utterly destroy" .)