Maybe cat on railway crossing provided scare (7)
I believe the answer is:
petrify
'scare' is the definition.
(thesaurus)
'maybe cat on railway crossing provided' is the wordplay.
'maybe cat' becomes 'pet' (cats are often kept as pets).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'railway' becomes 'ry' (abbreviation).
'crossing' is an insertion indicator (to cross can mean to go over or around).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'ry' enclosing 'if' is 'rify'.
'pet'+'rify'='PETRIFY'
(Other definitions for petrify that I've seen before include "Turn to stone" , "Paralyse with fear" , "Scare stiff" , "Frighten stiff" .)