A modern word meaning "again" (4)
I believe the answer is:
anew
'again' is the definition.
(synonyms)
'a modern' is the wordplay.
'modern' becomes 'new' (synonyms).
'a'+'new'='ANEW'
'word meaning' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for anew that I've seen before include "Once more (poetic)" , "From the beginning again" , "Again but differently" , "Afresh" , "Wane in a different way, again" .)