Only half of Spanish football team in field (5)
I believe the answer is:
realm
'field' is the definition.
(I know that realm is a type of field)
'only half of spanish football team' is the wordplay.
'only half of' means to take half the letters.
'spanish football team' becomes 'real madrid' (I've seen this before).
'realmadrid' halved is 'REALM'.
'in' is the link.
(Other definitions for realm that I've seen before include "the UK, perhaps" , "Kingdom's" , "Area of influence" , "King's domain" , "World" .)