Cook may interrogate thus (5)
I believe the answer is:
grill
This could be a double definition.
'cook' is the first definition.
(grilling is a form of cooking)
'interrogate thus' is the second definition.
'grill' can be an answer for 'interrogate' (I've seen this in other clues). I am not sure about the 'thus' bit.
'may' acts as a link.
Can you help me to learn more?
(Other definitions for grill that I've seen before include "Screen" , "Question; cook" , "Question closely" , "Broil" , "rack" .)