Philistine rune translated on sunny day (9)
I believe the answer is:
unrefined
'philistine' is the definition.
(thesaurus)
'rune translated on sunny day' is the wordplay.
'translated' indicates anagramming the letters.
'on' says to put letters next to each other.
'sunny' becomes 'fine' (I've seen this before).
'day' becomes 'd' (abbreviation for day).
'rune' with letters rearranged gives 'unre'.
'unre'+'fine'+'d'='UNREFINED'
(Other definitions for unrefined that I've seen before include "Rough" , "rude" , "Crude" , "Coarse" .)