Regattas regularly supplying food (4)
I believe the answer is:
eats
'food' is the definition.
(eats is a kind of food)
'regattas regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'regattas' are 'EATS'.
'supplying' acts as a link.
(Other definitions for eats that I've seen before include "snacks" , "Victuals" , "Food (slang)" , "Food (colloq.)" , "Commonly, they eliminate" .)