Furtive fish goes between rocks (8)
I believe the answer is:
sideways
'furtive' is the definition.
Both the definition and answer are adjectives. Perhaps there's a link between them I don't understand?
'fish goes between rocks' is the wordplay.
I cannot quite understand how this works, but
'fish' could be 'ide' (I've seen this before) and 'ide' is found in the answer.
The remaining letters 'sways' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sideways that I've seen before include "Askance" , "Lateral movement" , "Obliquley, crabwise" , "Not backwards or forwards" , "Movement of crab" .)