At holiday times it may be busy or in repose (6)
I believe the answer is:
resort
'at holiday times it may be busy' is the definition.
I can't judge whether this defines the answer.
'or in repose' is the wordplay.
'in' is an insertion indicator.
'repose' becomes 'rest' (synonyms).
'or' placed within 'rest' is 'RESORT'.
Can you help me to learn more?
(Other definitions for resort that I've seen before include "About to arrange" , "Place much frequented" , "site for recreation" , "Source of help - holiday location" , "Spa perhaps" .)