The fathead felt unwell and did badly (6)
I believe the answer is:
failed
'did badly' is the definition.
The definition and answer can be both to do with social activities as well as being past participle verbs.
Perhaps you can see an association between them that I can't see?
'the fathead felt unwell' is the wordplay.
'the fathead' becomes 'f' (head letter of 'fat').
'felt unwell' becomes 'ailed' (I've seen this in another clue).
'f'+'ailed'='FAILED'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for failed that I've seen before include "Didn't make it - not well" , "Bankrupt" , "Was unsuccessful, did not pass exam" , "Did not succeed, perhaps at exam" , "Didn't succeed" .)