Wading bird changes colour (9)
I believe the answer is:
turnstone
'wading bird' is the definition.
(turnstone is a kind of wading bird)
'changes colour' is the wordplay.
'changes' becomes 'turns' (turning is a kind of changing).
'colour' becomes 'tone' (tone can mean a colour or shade).
'turns'+'tone'='TURNSTONE'
(Other definitions for turnstone that I've seen before include "Relative of sandpiper, named for how it seeks food" , "Small short-billed sandpiper" , "Shore bird" , "Sort of sandpiper" , "Wader" .)