One’s unusual menu is not susceptible to complaint? (6)
I believe the answer is:
immune
'not susceptible to complaint?' is the definition.
I can't tell whether this defines the answer.
'one's unusual menu' is the wordplay.
'one's' becomes 'I'm' ('one is' is a formal way of saying 'I am').
'unusual' indicates anagramming the letters.
'menu' with letters rearranged gives 'mune'.
'im'+'mune'='IMMUNE'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for immune that I've seen before include "Not subject or liable to" , "Exempt, secured against" , "Not susceptible to, say after inoculation" , "Not liable to, perhaps disease" , "Safe from infection etc" .)