Leave old power tool for duck (9)
I believe the answer is:
goosander
'for duck' is the definition.
(goosander is a kind of duck)
'leave old power tool' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'power tool' becomes 'sander' (sander is a kind of power tool).
'go'+'o'+'sander'='GOOSANDER'
(Other definitions for goosander that I've seen before include "duck" , "Bird" , "Waterbird" .)