Relax after the day before going up the mountain (7)
I believe the answer is:
everest
'the mountain' is the definition.
(thesaurus)
'relax after the day before' is the wordplay.
'relax' becomes 'rest' (I've seen this before).
'after' is a charade indicator (letters next to each other).
'the day before' becomes 'eve' (I've seen this before).
'rest' after 'eve' is 'EVEREST'.
'going up' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for everest that I've seen before include "The highest mountain of all (7)" , "High mountain" , "Himalayan mount" , "A high spot" , "Tee revs up the mountain" .)