A goose — look! (6)
I believe the answer is:
gander
This clue is a double definition.
'a goose' is the first definition.
(gander is a kind of goose)
'look' is the second definition.
(informal term for a look or glance)
(Other definitions for gander that I've seen before include "Looking at something - ranged (anag)" , "Male goose - quick look" , "Male goose; look (colloq.)" , "glance" , "Male bird - look" .)