Rising when expected, I subsequently hit back (9)
I believe the answer is:
retaliate
'hit back' is the definition.
(I've seen this before)
'rising when expected i subsequently' is the wordplay.
'rising' shows that the letters should be reversed in order (going up in a down clue).
'when expected' becomes 'ETA' (estimated time of arrival).
'subsequently' becomes 'later' (subsequently means later on).
'eta'+'i'+'later'='etailater'
'etailater' reversed gives 'RETALIATE'.
(Other definitions for retaliate that I've seen before include "Get revenge" , "Make tit-for-tat attack" , "settle accounts" , "Attack in return for attack" , "Return like for like" .)