Light-hearted person laughs at young friend's unfashionable loafers to begin with (7)
I believe the answer is:
playful
'light-hearted' is the definition.
(I've seen this before)
'person laughs at young friend's unfashionable loafers to begin with' is the wordplay.
'to begin with' indicates taking the first letters.
The first letters of 'person laughs at young friends unfashionable loafers' is 'PLAYFUL'.
(Other definitions for playful that I've seen before include "Teasing, unserious" , "Full of fun" , "Fun-loving" , "Frolicsome" , "Lively" .)