Thought of euphemism finally: 'pre-loved' (5)
I believe the answer is:
mused
'thought of' is the definition.
(I've seen this before)
'euphemism finally pre-loved' is the wordplay.
'finally' indicates one should take the final letters.
'pre-loved' becomes 'used' (I've seen this before).
The last letter of 'euphemism' is 'm'.
'm'+'used'='MUSED'
(Other definitions for mused that I've seen before include "Fuddled" , "Was absorbed in thought" , "Reflected or pondered" , "Contemplated" , "Closer" .)