Young dog, hard at work when rodent emerges (9,3)
I believe the answer is:
groundhog day
'rodent emerges' is the definition.
I can't judge whether this definition defines the answer.
'young dog hard at work' is the wordplay.
'at work' indicates an anagram.
'young'+'dog'+'hard'='youngdoghard'
'youngdoghard' is an anagram of 'GROUNDHOG DAY'.
'when' is the link.
Can you help me to learn more?
(Other definitions for groundhog day that I've seen before include "Situation in which events are continually repeated" , "Picture" .)