Initial rifts develop (5)
I believe the answer is:
first
'initial' is the definition.
(similar in meaning)
'rifts develop' is the wordplay.
'develop' indicates anagramming the letters.
'rifts' is an anagram of 'FIRST'.
(Other definitions for first that I've seen before include "Pre-eminent" , "Premier (except in football!)" , "in dominant position" , "Rifts of supreme sort" , "at the outset" .)