Mention many a new tie (4)
I believe the answer is:
cite
'mention' is the definition.
(synonyms)
'many a new tie' is the wordplay.
'many' becomes 'c' (C is the Roman numeral for 100).
'a new' is an anagram indicator.
'tie' anagrammed gives 'ite'.
'c'+'ite'='CITE'
(Other definitions for cite that I've seen before include "Give as an example" , "Quote (a reference)" , "Summon - quote" , "Make reference to" , "Quote (an author)" .)