Attempt to change eel's gender (5)
I believe the answer is:
foray
'attempt' is the definition.
(I know that foray is a type of attempt)
'to change eel's gender' is the wordplay.
I cannot quite see how this works, but
'to' could be 'for' and 'for' is located in the answer.
The remaining letters 'ay' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for foray that I've seen before include "Brief attack" , "Raid or incursion" , "Raid for plunder" , "Depredation" , "Brief incursion" .)