Sets of nine goals crushing national team essentially (7)
I believe the answer is:
enneads
'sets of nine' is the definition.
'goals crushing national team essentially' is the wordplay.
'goals' becomes 'ends' ('end' can be a synonym of 'goal').
'crushing' indicates putting letters inside.
'national' becomes 'n' (abbreviation listed in Chambers).
'essentially' indicates the central letters.
The middle letters of 'team' are 'ea'.
'n'+'ea'='nea'
'ends' enclosing 'nea' is 'ENNEADS'.
(Other definitions for enneads that I've seen before include "Sane end (anag.)" , "Groups with members one over the eight" , "groups of nine" , "Eights plus coxes, perhaps" , "Groups appearing one over the eight" .)