Philistine's job, on the other hand, is a fake (8)
I believe the answer is:
impostor
'a fake' is the definition.
('impostor' can be a synonym of 'fake')
'philistine's job on the other hand' is the wordplay.
I cannot really understand how this works, but
'job' could be 'post' (post is a kind of job) and 'post' is present in the answer.
'on' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for impostor that I've seen before include "One who isn't what he claims to be" , "type of triumph for Kipling, for example" , "Charlatan - is to romp (anag)" , "Fake figure" , "phoney!" .)