Wading bird initially watched by French priest crossing lake (6)
I believe the answer is:
curlew
'wading bird' is the definition.
(curlew is a kind of wading bird)
'initially watched by french priest crossing lake' is the wordplay.
'initially' suggests taking the first letters.
'by' is a charade indicator (letters next to each other).
'french priest' becomes 'cure' (French for 'priest').
'crossing' indicates putting letters inside.
'lake' becomes 'l'.
The initial letter of 'watched' is 'w'.
'cure' placed around 'l' is 'curle'.
'w' after 'curle' is 'CURLEW'.
(Other definitions for curlew that I've seen before include "Large shorebird" , "Wader with downcurved bill" , "Wader with curved bill" , "Wading bird with long slender curved bill" , "Curve-beaked bird" .)