Problem solver when things heat up (6)
I believe the answer is:
summer
'heat up' is the definition.
Although both the answer and definition are verbs in their base form, I don't understand how they can define each other.
'problem solver when' is the wordplay.
'problem' becomes 'sum' (arithmetic problem).
'solver when' becomes 'mer' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sum'+'mer'='SUMMER'
'things' is the link.
Can you help me to learn more?
(Other definitions for summer that I've seen before include "Warm season, allegedly" , "year" , "Period of heat" , "Beam" , "See 10" .)