The rose is now seen as lacking the symbol of love (4)
I believe the answer is:
eros
'symbol of love' is the definition.
(I've seen this in another clue)
'the rose is now seen as lacking' is the wordplay.
'the rose' says the letters should be written backwards.
'is now seen' becomes 'sor' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'as' becomes 'eg' (both can introduce an example).
'lacking' means to remove the last letter (the word is incomplete or lacking).
'eg' with its last letter removed is 'e'.
'sor'+'e'='sore'
'sore' in reverse letter order is 'EROS'.
'the' is the link.
Can you help me to learn more?
(Other definitions for eros that I've seen before include "London landmark" , "Deity" , "Statue of love-god in Piccadilly Circus in London" , "Greek god of love - see statue in Piccadilly" , "Cupid, to the Greeks" .)