Crossword Genius

Delve rigorously with youngster (5)

Ross

I believe the answer is:

elver

'youngster' is the definition.
(I have seen 'Slippery youngster' mean 'elver' so perhaps 'youngster' could also mean 'elver')

'delve rigorously with' is the wordplay.
'with' says the answer is hidden in the clue.
'ELVER' is hidden within 'delve rigorously'.

(Other definitions for elver that I've seen before include "Young slippery fish" , "Little fish" , "Immature eel" , "Young migratory fish" , "Young swimmer" .)

I've seen this clue in The Mirror.
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