Symbol of love very touching, in retrospect (4)
I believe the answer is:
eros
'symbol of love' is the definition.
(I've seen this in another clue)
'very touching in retrospect' is the wordplay.
'very' becomes 'so' (both can mean 'extremely').
'touching' becomes 're' (both can mean concerning or relating to).
'in retrospect' is a reversal indicator (in retrospect means looking back).
'so'+'re'='sore'
'sore' written backwards gives 'EROS'.
(Other definitions for eros that I've seen before include "Arrow shooter" , "Sore about love god" , "Deity" , "Circus boy" , "Orbiter" .)