Said angrily “It spluttered when cooking” (4)
I believe the answer is:
'spluttered when cooking' is the definition.
I can't judge whether this defines the answer.
'said angrily it' is the wordplay.
'said angrily' becomes 'spa' (I can't justify this - if you can you should give a lot more credence to this answer).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
Can you help me to learn more?
(Other definitions for spat that I've seen before include "Slight argument" , "Pat's involved in petty quarrel" , "Contretemps" , "angry words" , "Bickering" .)