Wander by rock face to find duck (7)
I believe the answer is:
gadwall
'duck' is the definition.
(I've seen this before)
'wander by rock face' is the wordplay.
'wander' becomes 'gad' (gadding is a kind of wandering).
'by' means one lot of letters go next to another.
'rock face' becomes 'wall' (a wall of rock).
'gad'+'wall'='GADWALL'
'to find' acts as a link.
(Other definitions for gadwall that I've seen before include "Type of duck" , "bird" , "Mallard-type duck" , "Duck related to the mallard" .)