Pressure to stop mail while away (5)
I believe the answer is:
spend
'while away' is the definition.
(thesaurus)
'pressure to stop mail' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'to stop' is an insertion indicator.
'mail' becomes 'send' ('send' can be a synonym of 'mail').
'p' placed inside 'send' is 'SPEND'.
(Other definitions for spend that I've seen before include "Pass (time) in a specified way" , "Pay out (on goods)" , "Outlay" , "Blue" , "While away" .)