Disturb forged steel nut (8)
I believe the answer is:
unsettle
'disturb' is the definition.
(I've seen this before)
'forged steel nut' is the wordplay.
'forged' is an anagram indicator.
'steel'+'nut'='steelnut'
'steelnut' anagrammed gives 'UNSETTLE'.
(Other definitions for unsettle that I've seen before include "worry" , "'Disturb, make uneasy (8)'" , "Throw" , "'Disturb, unnerve (8)'" , "Faze" .)