Stops blowing top and relaxes (5)
I believe the answer is:
eases
'relaxes' is the definition.
(ease can mean to relax or reduce)
'stops blowing top' is the wordplay.
'stops' becomes 'ceases' ('cease' can be a synonym of 'stop').
'blowing top' means to remove the first letter.
'ceases' with its initial letter taken off is 'EASES'.
'and' is the link.
(Other definitions for eases that I've seen before include "provides relief" , "Moves carefully" , "Relieves, loosens" , "Facilitates" , "Lessens tensions" .)