It's silly to be tough on a fathead (9)
I believe the answer is:
foolhardy
'it's silly' is the definition.
(thesaurus)
'tough on a fathead' is the wordplay.
'tough' becomes 'hardy' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'a fathead' becomes 'fool' (I can't justify this - if you can you should believe this answer much more).
'hardy' put after 'fool' is 'FOOLHARDY'.
'to be' is the link.
Can you help me to learn more?
(Other definitions for foolhardy that I've seen before include "Impulsive" , "daredevil" , "Dry loofah for quality of rashness" , "Bold" , "Rash - incautious" .)