Male's small jumper with shortened back (7)
I believe the answer is:
rooster
'male's' is the definition.
(male chicken)
'small jumper with shortened back' is the wordplay.
'small jumper' becomes 'roo' (short for kangaroo, something which jumps; 'small' indicates a short form).
'with' says to put letters next to each other.
'shortened' means to remove the last letter.
'back' becomes 'stern' (stern is a kind of back).
'stern' with its last letter taken away is 'ster'.
'roo'+'ster'='ROOSTER'
(Other definitions for rooster that I've seen before include "Farmyard fowl" , "So retro (anag.)" , "Cockerel (mainly US)" , "American cockerel" , "Crowing bird" .)