Resistance, with support, absorbing pressure without delay (5)
I believe the answer is:
rapid
'without delay' is the definition.
'resistance with support absorbing pressure' is the wordplay.
'resistance' becomes 'r' (abbreviation).
'with' means one lot of letters go next to another.
'support' becomes 'aid' (aiding is a kind of supporting).
'absorbing' means one lot of letters goes inside another.
'pressure' becomes 'p' (abbreviation).
'aid' placed around 'p' is 'apid'.
'r'+'apid'='RAPID'
(Other definitions for rapid that I've seen before include "Speedy (5)" , "haste" , "Waterway where the current runs very fast" , "Speedy, quick" , "Happening at great speed" .)