About relaxation, it's the very top (5)
I believe the answer is:
crest
'the very top' is the definition.
'about relaxation' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'relaxation' becomes 'rest' ('rest' can be a synonym of 'relaxation').
'c'+'rest'='CREST'
'it's' is the link.
(Other definitions for crest that I've seen before include "Tuft" , "Top (of wave etc)" , "Summit - emblem - cockscomb" , "Top of a ridge or wave" , "Top point of hill or wave" .)