Argument about recipe: he and his wife had very varying dietary tastes (5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

SPAT (argument) round R (recipe) – Jack Sprat, according to the nursery rhyme, could eat no fat while his wife could eat no lean (To forestall a possible query about R = recipe – it seems a little while since we had one – ‘recipe’ is Latin for ‘take’ and the abbreviation R was formerly found on doctors’ prescriptions)