Large body: ton in short dress (4)
I believe the answer is:
star
'large body' is the definition.
'star' can be an answer for 'body' (I have seen 'Celestial body' mean 'star' so perhaps 'body' could also mean 'star'). I am unsure of the 'large' bit.
'ton in short dress' is the wordplay.
'ton' becomes 't' (abbreviation).
'in' indicates putting letters inside.
'short dress' becomes 'sar' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
't' going inside 'sar' is 'STAR'.
Can you help me to learn more?
(Other definitions for star that I've seen before include "chamber" , "Glamorous celebrity" , "White blaze on a horse's forehead" , "Eg, Betelgeuse" , "Heavenly apparition" .)