Be in a rut, possibly; nevertheless deny (5)
I believe the answer is:
rebut
'nevertheless deny' is the definition.
'rebut' can be an answer for 'deny' (to rebut is to deny or refute). I'm not certain of the 'nevertheless' bit.
'be in a rut' is the wordplay.
'be' becomes 'eb' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'eb' inserted inside 'rut' is 'REBUT'.
'possibly' acts as a link.
Can you help me to learn more?
(Other definitions for rebut that I've seen before include "Drive back" , "Contradict or disprove" , "Prove to be false or incorrect" , "Give the lie to" , "Refute - disprove" .)