Cautious head ignoring answer's sardonic humour (7)

'cautious' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I can't see?

'head ignoring answer's sardonic humour' is the wordplay.
I cannot really see how this works, but
'head' could be 'ness' (both can mean a promontory) and 'ness' is present in the answer.
'sardonic' could be 'wry' (I've seen this before) and 'wry' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?