Unit reformed our sailors, one after another (2,4)
I believe the answer is:
in turn
'one after another' is the definition.
(in turn means one by one)
'unit reformed our sailors' is the wordplay.
'reformed' is an anagram indicator.
'our sailors' becomes 'RN' (Royal Navy).
'unit' anagrammed gives 'intu'.
'intu'+'rn'='IN TURN'
(Other definitions for in turn that I've seen before include "in an orderly fashion" , "not out of place" , "One after another" , "a succession of things happen" , "orderly treatment" .)