Measure of cycles is very painful, reportedly? (9)
I believe the answer is:
megahertz
'measure of cycles' is the definition.
(a Hertz is equal to one cycle per second)
'very painful reportedly?' is the wordplay.
I cannot quite understand how this works, but
'very' could be 'mega' (I've seen this before) and 'mega' is present in the answer.
'reportedly?' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'is' is the link.
(Another definition for megahertz that I've seen is " MHz in full".)