Central American new in polo, perhaps to finish first (8)
I believe the answer is:
dominant
'central' is the definition.
(thesaurus)
'american new in polo perhaps to finish first' is the wordplay.
'american new' becomes 'an' (this might be a standard abbreviation which I don't know about).
'in' means one lot of letters goes inside another.
'polo perhaps' becomes 'mint' (Polo is a brand of mints).
'to finish' becomes 'do'.
'first' says to put letters next to each other.
'an' inserted into 'mint' is 'minant'.
'minant' after 'do' is 'DOMINANT'.
(Other definitions for dominant that I've seen before include "Like a boss" , "Prevailing or in a commanding position" , "note?" , "Most influential; fifth of scale" , "Most important or powerful" .)