When users get upset about short measure, they can be hot! (7)
I believe the answer is:
summers
'measure they can be hot' is the definition.
The definition suggests an adverb but the answer is not.
'when users get upset about' is the wordplay.
'when' becomes 'mm' (I can't explain this - if you can you should give a lot more credence to this answer).
'get upset' indicates anagramming the letters (I've seen 'getting upset' mean this).
'about' is an insertion indicator.
'users' is an anagram of 'suers'.
'mm' placed into 'suers' is 'SUMMERS'.
'short' is the link.
Can you help me to learn more?
(Other definitions for summers that I've seen before include "warmer weather!" , "Seasons" , "They add up" .)