First breaks, then splits! (5)
I believe the answer is:
rifts
'splits' is the definition.
(I've seen this before)
'first breaks' is the wordplay.
'breaks' is an anagram indicator.
'first' is an anagram of 'RIFTS'.
'then' is the link.
(Other definitions for rifts that I've seen before include "differences ..." , "Deep divides" , "Clefts or fissures." , "Schisms" , "Breaks, severances" .)