Number in the Spanish uniform (6)
I believe the answer is:
eleven
'number' is the definition.
(eleven is a kind of number)
'the spanish uniform' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'uniform' becomes 'even' (uniform can mean even or level).
'el'+'even'='ELEVEN'
'in' acts as a link.
(Other definitions for eleven that I've seen before include "Odd number for a team" , "Number, on a team perhaps" , "Number on a side (6)" , "Time for the mid-morning tea break?" , "XI as Roman numeral" .)