Abridge on regular basis — that’s important (3)
I believe the answer is:
big
'important' is the definition.
(similar in meaning)
'abridge on regular basis' is the wordplay.
'on regular basis' indicates alternate letters (letters selected at regular intervals).
The alternating letters of 'abridge' are 'BIG'.
'that's' acts as a link.
(Other definitions for big that I've seen before include "Circus tent" , "Sizeable" , "Massive" , "oversized" , "Of considerable size" .)