One who may thrive on complaints (6)
I believe the answer is:
doctor
'one who' is the definition.
(from 'Doctor Who', the famous TV series)
'thrive on complaints' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'to' and 'to' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'may' acts as a link.
Can you help me to learn more?
(Other definitions for doctor that I've seen before include "Medical professional or university don" , "Medical worker or holder of highest university degree" , "bones" , "Medic or holder of highest university degree" , "Medical specialist" .)