Calm and secure during blow (7)
I believe the answer is:
patient
'calm' is the definition.
(I've seen this before)
'secure during blow' is the wordplay.
'secure' becomes 'tie' (tying is a kind of securing).
'during' is an insertion indicator.
'blow' becomes 'pant'.
'tie' going into 'pant' is 'PATIENT'.
'and' is the link.
(Other definitions for patient that I've seen before include "Not easily provoked" , "Sufferer" , "Calmly enduring like hospital inmate" , "Person requiring medical care" , "case for treatment" .)