Relaxes when in view on the way up (5)
I believe the answer is:
eases
'relaxes' is the definition.
(I've seen this before)
'when in view on the way up' is the wordplay.
'when' becomes 'as'.
'in' is an insertion indicator.
'view' becomes 'see' ('see' can be a synonym of 'view').
'on the way up' says the letters should be written in reverse.
'see' backwards is 'ees'.
'as' going into 'ees' is 'EASES'.
(Other definitions for eases that I've seen before include "Assuages or slackens" , "Alleviates, relieves" , "Relieves, loosens" , "Softens" , "Borders, margins" .)