Clarify to judge in Spain (6)
I believe the answer is:
refine
'clarify' is the definition.
(I've seen this in another clue)
'judge in spain' is the wordplay.
'judge' becomes 'ref' (referee).
'spain' becomes 'e' (abbreviation for Espana).
'ref'+'in'+'e'='REFINE'
'to' acts as a link.
(Other definitions for refine that I've seen before include "Remove impurities or make cultured" , "Cleanse from impurities" , "Purify or make more cultured" , "Make pure" , "Remove impurities from (eg, metals)" .)