Time soon modifies feelings (8)
I believe the answer is:
emotions
'feelings' is the definition.
(emotion is a kind of feeling)
'time soon modifies' is the wordplay.
'modifies' indicates anagramming the letters (I've seen 'modified' mean this).
'time'+'soon'='timesoon'
'timesoon' with letters rearranged gives 'EMOTIONS'.
(Other definitions for emotions that I've seen before include "Passions" , "Intense mental feelings, like love or hate" , "Feelings provoked by noise, Tom" , "Strong feelings" , "instinctive feelings" .)