At rocky height, check lighter (5)
I believe the answer is:
torch
'lighter' is the definition.
(thesaurus)
'at rocky height check' is the wordplay.
'at' is a charade indicator (letters next to each other).
'rocky height' becomes 'tor' (I've seen this before).
'check' becomes 'ch' (abbreviation).
'tor'+'ch' is 'TORCH'.
(Other definitions for torch that I've seen before include "Portable light; burn" , "Source of light" , "Set fire to - hand-held light" , "Set alight deliberately" , "Set fire to; electric lamp" .)