Under pressure after spat about verb form (4,5)
I believe the answer is:
past tense
'verb form' is the definition.
'under pressure after spat about' is the wordplay.
'under pressure' becomes 'tense' (I've seen this before).
'after' means one lot of letters go next to another.
'about' indicates anagramming the letters.
'spat' is an anagram of 'past'.
'tense' after 'past' is 'PAST TENSE'.
(Other definitions for past tense that I've seen before include "Was perhaps" , "history?" , "It expresses something that has happened" , "Grammatical verb form" , "What could be perfect in a lesson of French" .)