Playing harp too much - it initially enrages deity (9)
I believe the answer is:
aphrodite
'deity' is the definition.
(I know that Aphrodite is a Greek deity)
'playing harp too much it initially enrages' is the wordplay.
'playing' is an anagram indicator.
'too much' becomes 'od' (abbreviation for overdose).
'initially' indicates taking the first letters.
The initial letter of 'enrages' is 'e'.
'harp' anagrammed gives 'aphr'.
'aphr'+'od'+'it'+'e'='APHRODITE'
(Other definitions for aphrodite that I've seen before include "Greek goddess of beauty and love" , "got Paris's approval" , "Paris gave her an apple" , "Greek goddess equivalent to Roman Venus" , "Atrophied (anag.)" .)