Quail a bit when crossing lake (5)
'quail' is the definition.
(term for the American quail)
'a bit when crossing lake' is the wordplay.
'a bit' becomes 'coin' (old-fashioned term for a coin).
'when crossing' is an insertion indicator.
'lake' becomes 'l'.
'coin' going around 'l' is 'COLIN'.
(Other definitions for colin that I've seen before include "--- Wilson, Eng. writer (The Outsider)", "Man's name".)