Pen new melody for deity (7)
I believe the answer is:
neptune
'for deity' is the definition.
(Neptune is an example)
'pen new melody' is the wordplay.
'new' indicates an anagram.
'melody' becomes 'tune' (synonyms).
'pen' with letters rearranged gives 'nep'.
'nep'+'tune'='NEPTUNE'
(Other definitions for neptune that I've seen before include "King of the sea" , "heavenly body" , "one of the Planets" , "Planet, identified 1846" , "Eighth rock from the Sun" .)