Type of betting established inequality (5,4)

I believe the answer is:

fixed odds

'type of betting' is the definition.
(I've seen this before)

'established inequality' is the wordplay.
'established' becomes 'fixed' (fixing is a kind of establishing).
'inequality' becomes 'odds' (I've seen this before).
'fixed'+'odds'='FIXED ODDS'

(Another definition for fixed odds that I've seen is " Type of betting".)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app