Leaving the mountain when there is less traffic (3-4)
I believe the answer is:
'there is less traffic' is the definition.
I can't tell whether this definition defines the answer.
'leaving the mountain' is the wordplay.
'leaving' becomes 'off' ('I'm off' means 'I'm leaving').
'the mountain' becomes 'peak' (the peak of a mountain).
'when' is the link.
Can you help me to learn more?
(Other definitions for off-peak that I've seen before include "Outside the times when demand is greatest" , "Less busy (time)" , "Time when tickets are usually cheaper" , "Fake fop (anag.)" , "At a time when demand is less" .)