Hurricane lamp in stern, normal tradition, originally, at sea (5,7)
I believe the answer is:
storm lantern
'hurricane lamp' is the definition.
(synonyms)
'stern normal tradition originally at sea' is the wordplay.
'originally' says to take the initial letters.
'at sea' indicates an anagram.
The first letter of 'tradition' is 't'.
'stern'+'normal'+'t'='sternnormalt'
'sternnormalt' anagrammed gives 'STORM-LANTERN'.
'in' acts as a link.
(Other definitions for storm lantern that I've seen before include "lighting" , "Hurricane lamp" , "illumination in troubled times?" .)