Bishop put on weight in spring (6)
I believe the answer is:
bounce
'spring' is the definition.
(I know that spring can be written as bounce)
'bishop put on weight' is the wordplay.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'put on' means one lot of letters go next to another.
'weight' becomes 'ounce' (unit of weight).
'b'+'ounce'='BOUNCE'
'in' acts as a link.
(Other definitions for bounce that I've seen before include "Showing self-confidence" , "Exuberance; rebound" , "Reflect back from a surface" , "Spring back after impact" , "Rebound; self-confidence" .)