Sat around after dance and put on weight (7)
I believe the answer is:
ballast
'put on weight' is the definition.
'ballast' can be an answer for 'weight' (I've seen this before). I am not certain of the 'put on' bit.
'sat around after dance' is the wordplay.
'around' indicates an anagram.
'after' means one lot of letters go next to another.
'dance' becomes 'ball' (ball is a kind of dance).
'sat' anagrammed gives 'ast'.
'ast' after 'ball' is 'BALLAST'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for ballast that I've seen before include "Steadying weight found at balls" , "Heavy stuff used to stabilise boat" , "Heavy material taken aboard to steady ship" , "Mass giving ship stability" , "Balloon steadier" .)