Call the silly man an egghead! (4)
I believe the answer is:
name
'call' is the definition.
(synonyms)
'the silly man an egghead' is the wordplay.
'the silly' is an anagram indicator.
'an egghead' becomes 'e' (head letter of 'egg').
'man' with letters rearranged gives 'nam'.
'nam'+'e'='NAME'
(Other definitions for name that I've seen before include "Title, term" , "By which a person is known" , "Moniker" , "Famous person; reputation" , "Mean sort of appellation" .)