Nimble mole torn apart by rook (4)
I believe the answer is:
spry
'nimble' is the definition.
('spry' can be a synonym of 'nimble')
'mole torn apart by rook' is the wordplay.
I cannot quite understand how this works, but
'rook' could be 'r' (abbreviation in chess) and 'r' is present in the answer.
'mole' could be 'spy' (I've seen this before) and 'spy' is found in the leftover letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for spry that I've seen before include "Fleet" , "Quick and agile" , "Nimble, brisk" , "Light on one's feet" , "Agile (for one's age?)" .)