That man about to get taken aback for a time (5)
I believe the answer is:
epoch
'time' is the definition.
(I know that epoch is a type of geologic time)
'that man about to get taken aback' is the wordplay.
'that man' becomes 'he' (he refers to a man).
'about' indicates putting letters inside.
'to get' becomes 'cop' (I've seen this before).
'taken aback' is a reversal indicator.
'he' enclosing 'cop' is 'hcope'.
'hcope' backwards is 'EPOCH'.
'for a' is the link.
(Other definitions for epoch that I've seen before include "extended period" , "Unit of geological time" , "Significant period" , "remarkable time" , "Aeon" .)