Dispute reaches many regulars (7)
I believe the answer is:
gainsay
'dispute' is the definition.
(I know that dispute can be written as gainsay)
'reaches many regulars' is the wordplay.
'reaches' becomes 'gains' ('gain' can be a synonym of 'reach').
'regulars' indicates alternate letters.
The alternate letters of 'many' are 'ay'.
'gains'+'ay'='GAINSAY'
(Other definitions for gainsay that I've seen before include "Contradict, deny, dispute" , "Challenge, dispute" , "Speak against" .)