Mention not getting a rise, masking pained expression (5,2)
I believe the answer is:
touch on
'mention' is the definition.
(touching on is a kind of mentioning)
'not getting a rise masking pained expression' is the wordplay.
'getting a rise' shows that the letters should be reversed in order (in a down clue, letters go up).
'masking' is an insertion indicator.
'pained expression' becomes 'ouch' (I've seen this before).
'not' in reverse letter order is 'ton'.
'ton' going around 'ouch' is 'TOUCH ON'.
(Another definition for touch on that I've seen is " Mention briefly in tactile manner?".)