Apply soothing balm or aggravate one's trouble (3,2,2)
I believe the answer is:
rub it in
'apply soothing balm or aggravate' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'one's trouble' is the wordplay.
I cannot quite see how this works, but
'trouble' could be 'rub' (I've seen this before) and 'rub' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
The remaining letters 'tin' 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?
(Other definitions for rub it in that I've seen before include "Remind person of unpleasant fact - during massage?" , "Remind or taunt someone about unpleasant fact" , "Unkindly emphasise" , "Continue to remind one of a mistake" , "Harp on something distasteful to person not wishing to be reminded of it" .)