Clue: Cut up nothing, devouring game earnestly (2,5)
Answer: EX ANIMO
Explanation: Definition: earnestly
An envelope ('devouring') of NIM ('game'; this matchstick game came up not so long ago, but I have not yet tracked down where, even though I commented on it – the only reference I could find was to a Qaos puzzle that I blogged in 2017) in EXA, a reversal ('up' in a down light) of AXE ('cut'); plus O ('nothing').