Respite allowed initially under pressure (3-2)
I believe the answer is:
let-up
'respite' is the definition.
(I've seen this before)
'allowed initially under pressure' is the wordplay.
'allowed' becomes 'let' (to let is to allow or permit).
'initially' indicates taking the first letters.
The first letters of 'under pressure' is 'up'.
'let'+'up'='LET-UP'
(Other definitions for let-up that I've seen before include "Relieving pause" , "Pause in intensity" , "Abatement" , "Pause, temporary respite" , "Decline" .)