Hemp used in making sails (5)
I believe the answer is:
sisal
'hemp' is the definition.
(I've seen this in another clue)
'making sails' is the wordplay.
'making' indicates an anagram.
'sails' anagrammed gives 'SISAL'.
'used in' acts as a link.
(Other definitions for sisal that I've seen before include "Rope fibre from leaves of tropical plant" , "Agave rope-fibre" , "Agave yielding fibre" , "Fibre of Mexican agave" , "Hemp fibre" .)