Tropical lake originally accommodating green fish? (5)
I believe the answer is:
trawl
'fish?' is the definition.
(trawl can mean to fish)
'tropical lake originally accommodating green' is the wordplay.
'originally' suggests taking the first letters.
'accommodating' is an insertion indicator.
'green' becomes 'raw' (both can mean naive or inexperienced).
The initial letters of 'tropical lake' is 'tl'.
'tl' placed around 'raw' is 'TRAWL'.
(Other definitions for trawl that I've seen before include "Catch" , "Fishing-net" , "Large wide-mouthed fishing net, usually dragged" , "Large net used for fishing" , "Go fishing" .)