Charity given by early mass regulars (4)
I believe the answer is:
alms
'charity' is the definition.
(alms is a kind of charity)
'early mass regulars' is the wordplay.
'regulars' means one should take alternating letters (letters selected at regular intervals).
'early'+'mass'='earlymass'
The alternate letters of 'earlymass' are 'ALMS'.
'given by' acts as a link.
(Other definitions for alms that I've seen before include "Contributions to the poor" , "Charitable donations to the needy" , "Money given to poor people" , "Charitable gifts - slam them" , "Charitable offering" .)