Time soon alters feelings (8)
I believe the answer is:
emotions
'feelings' is the definition.
(emotion is a kind of feeling)
'time soon alters' is the wordplay.
'alters' indicates an anagram.
'time'+'soon'='timesoon'
'timesoon' is an anagram of 'EMOTIONS'.
(Other definitions for emotions that I've seen before include "Intense mental feelings, like love or hate" , "Strong feelings" , "Passions" , "Anger and love, say" , "Feelings provoked by noise, Tom" .)