Even American clubs score to catch United (8)
I believe the answer is:
actually
'even' is the definition.
(both might be said by a speaker correcting himself)
'american clubs score to catch united' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'score' becomes 'tally' (tally is a kind of score**).
'to catch' means one lot of letters goes inside another.
'united' becomes 'u'.
'tally' placed around 'u' is 'tually'.
'a'+'c'+'tually'='ACTUALLY'
(Other definitions for actually that I've seen before include "A lay cult may be existing in fact" , "Really existing" , "In reality" , "As a matter of fact" , "Really, in fact" .)