Front of deserted vessel is gloomy (4)
I believe the answer is:
dark
'is gloomy' is the definition.
(similar in meaning)
'front of deserted vessel' is the wordplay.
'front of' indicates taking the first letters (the letter at the front of the word).
'vessel' becomes 'ark' (ark is a kind of vessel).
The initial letter of 'deserted' is 'd'.
'd'+'ark'='DARK'
(Other definitions for dark that I've seen before include "sinister and > bleak" , "With little or no light" , "Overcast" , "Secret, shadowed" , "Deprived of light" .)