Argument about recipe: he and his wife had very varying dietary tastes (5)
I believe the answer is:
sprat
'he and his wife had very varying dietary tastes' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'argument about recipe' is the wordplay.
'argument' becomes 'spat' (a spat is a disagreement or argument).
'about' indicates putting letters inside.
'recipe' becomes 'r' (abbreviation in medical prescriptions).
'spat' placed around 'r' is 'SPRAT'.
Can you help me to learn more?
(Other definitions for sprat that I've seen before include "chap giving richer course material to the Dutch" , "Traps (anag.)" , "'Set a . . . . . to catch a whale'" , "one on a fat-free diet" , "Couple sharing meat" .)