Again start to take for granted after loss of pressure (6)
I believe the answer is:
resume
'again start' is the definition.
(resume can mean to start doing something again)
'take for granted after loss of pressure' is the wordplay.
'take for granted' becomes 'presume' (to take for granted as true).
'after loss of' indicates named letters should be taken away.
'pressure' becomes 'p' (abbreviation).
'presume' with 'p' taken away is 'RESUME'.
'to' acts as a link.
(Other definitions for resume that I've seen before include "Continue after interruption" , "Re-open" , "Precis" , "Begin where you left off" , "Pick up again" .)