Nimble Scotsman’s left resisting (4)
I believe the answer is:
deft
'nimble' is the definition.
(thesaurus)
'scotsman's left resisting' is the wordplay.
'scotsman' becomes 'ian'.
'left' suggests deleting specific letters.
'resisting' becomes 'defiant'.
'defiant' with 'ian' taken away is 'DEFT'.
(Other definitions for deft that I've seen before include "Quick and skilful in movement" , "Quick and effective" , "Handling things skilfully or neatly" , "Adroit, dexterous" , "Clever" .)