Write uplifting melody for sea god (7)
I believe the answer is:
neptune
'sea god' is the definition.
(I've seen this before)
'write uplifting melody' is the wordplay.
'write' becomes 'pen' (synonyms).
'uplifting' says the letters should be written backwards.
'melody' becomes 'tune' (synonyms).
'pen' written backwards gives 'nep'.
'nep'+'tune'='NEPTUNE'
'for' is the link.
(Other definitions for neptune that I've seen before include "part of Planets Suite" , "musical work" , "Holst composed it" , "Holst piece" , "extract from The Planets" .)