Eagle I left in the water (6)
I believe the answer is:
aquila
'eagle' is the definition.
(I've seen this before)
'i left in the water' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in the' indicates putting letters inside.
'water' becomes 'aqua' (I've seen this before).
'i'+'l'='il'
'il' placed within 'aqua' is 'AQUILA'.
(Other definitions for aquila that I've seen before include "Altair's constellation" , "starry set" , "Italian city" , "group of stars" , "Type of birds" .)