Time on boat for rescuing a creature in river (5)
I believe the answer is:
tarka
'rescuing a creature in river' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'time on boat for' is the wordplay.
'time' becomes 't' (abbreviation).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'boat' becomes 'ark' (ark is a kind of boat).
'for' becomes 'a' (I can't explain this - if you can you should give a lot more credence to this answer).
't'+'ark'+'a'='TARKA'
Can you help me to learn more?
(Other definitions for tarka that I've seen before include "Devon swimmer" , "One after fish booked" , "Swimmer in story" , "- - the Otter by H Williamson" , "Fictional otter" .)