Splendid headgear -- almost everyone is after it (7)
I believe the answer is:
capital
'splendid' is the definition.
(thesaurus)
'headgear almost everyone is after it' is the wordplay.
'headgear' becomes 'cap' (cap is a kind of headgear).
'almost' means to remove the last letter (most of the word but not all of it).
'everyone' becomes 'all' (I've seen this before).
'is after' is a charade indicator (letters next to each other).
'all' with its final letter removed is 'al'.
'al' after 'it' is 'ital'.
'cap'+'ital'='CAPITAL'
(Other definitions for capital that I've seen before include "Madrid, say" , "Funds" , "A country's main city" , "Excellent - assets - first city" , "high in architecture" .)