Cruise initially in established cult (4)
I believe the answer is:
sect
'cult' is the definition.
(thesaurus)
'cruise initially in established' is the wordplay.
'initially' indicates taking the first letters.
'in' is an insertion indicator.
'established' becomes 'set'.
The initial letter of 'cruise' is 'c'.
'c' inserted inside 'set' is 'SECT'.
(Other definitions for sect that I've seen before include "Group of people with unusual religious beliefs" , "party" , "Religious splinter group" , "Dissenting division of a larger religious group" , "Small group with own religious beliefs" .)