Regular supporting the Spanish team (6)
I believe the answer is:
eleven
'team' is the definition.
(eleven is a kind of team)
'regular supporting the spanish' is the wordplay.
'regular' becomes 'even' ('even' can be similar in meaning to 'regular').
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'the spanish' becomes 'el'.
'even' after 'el' is 'ELEVEN'.
(Other definitions for eleven that I've seen before include "XI as Roman numeral" , "Number killed in the Peterloo massacre" , "Football side" , "Prime number" , "Not first team (6,6) - See 24" .)