Thrust in the back perhaps, mad to spin round (4)
I believe the answer is:
stab
'thrust' is the definition.
(I know that stab is a kind of the thrust)
'the back perhaps mad to spin round' is the wordplay.
I cannot really understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
The remaining letters 'sab' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for stab that I've seen before include "Rough guess; to knife" , "Attack with a knife" , "Wound with a dagger" , "Sudden sharp pain" , "Wound with blade" .)