Match involving four old clubs is undecided (9)
I believe the answer is:
equivocal
'undecided' is the definition.
(thesaurus)
'match involving four old clubs' is the wordplay.
'match' becomes 'equal' (synonyms).
'involving' means one lot of letters goes inside another.
'four' becomes 'IV' (Roman numerals).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'iv'+'o'+'c'='ivoc'
'equal' going around 'ivoc' is 'EQUIVOCAL'.
'is' is the link.
(Other definitions for equivocal that I've seen before include "uncertain" , "it's indefinite" , "Questionable" , "Ambiguous,can be interpreted in two ways" , "Dithering, evasive" .)