In which to have a peaceful dip? (12)
I believe the answer is:
pacificocean
'in which to' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'a peaceful dip?' is the wordplay.
'a peaceful' becomes 'pacific' (I've seen this before).
'dip?' becomes 'ocean' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pacific'+'ocean'='PACIFICOCEAN'
'have' is the link.
Can you help me to learn more?
(Another definition for pacificocean that I've seen is " World''s largest, deepest sea".)