Eggs or veal regularly served (3)
I believe the answer is:
ova
'eggs' is the definition.
(term for egg cells)
'or veal regularly served' is the wordplay.
'regularly served' means one should take alternating letters.
'or'+'veal'='orveal'
The alternating letters of 'orveal' are 'OVA'.
(Other definitions for ova that I've seen before include "Prerequisite for procreation" , "Potential life sources" , "Female egg-cells" , "Multiple Latin eggs" , "Likely end for Russian Fed cup players" .)