Saying a team has old money (5)
I believe the answer is:
axiom
'saying' is the definition.
(axiom is a kind of saying)
'a team has old money' is the wordplay.
'team' becomes 'xi' (eleven, a football team).
'has' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'money' becomes 'm' (abbreviation in economics).
'a'+'xi'+'o'+'m'='AXIOM'
(Other definitions for axiom that I've seen before include "fundamental principle" , "Clearly true statement" , "that goes without saying" , "Plainly true proposition" , "Self-evident statement" .)