An inflammation, but which one? Let's move on (2,2,4,2,2)
I believe the answer is:
it is what it is
'on' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'an inflammation but which one? let's move' is the wordplay.
I cannot really understand how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
'which' could be 'what' (I've seen this in other clues) and 'what' is located in the answer.
'one?' could be 'i' (Roman numeral) and 'i' is located in the answer.
'move' could be 'sit' (sitting is a kind of moving) and 'sit' is found within the leftover letters.
The remaining letters 'tis' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?