First of garments confined to waste, put something with a jumper on top (4,5)
I believe the answer is:
pogo stick
'something with a jumper on top' is the definition.
I can't tell whether this defines the answer.
'first of garments confined to waste put' is the wordplay.
'first of garments' becomes 'g' (pst letter of 'garments').
'confined to' means one lot of letters goes inside another.
'waste' becomes 'poo' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'put' becomes 'stick' (I've seen this in other clues).
'g' put within 'poo' is 'pogo'.
'pogo'+'stick'='POGO STICK'
Can you help me to learn more?
(Other definitions for pogo stick that I've seen before include "Jumping toy" , "Jumping rod with a spring" , "On which kids bounce along" .)