Penalty kick is hard, guys admitted (10)
I believe the answer is:
punishment
'penalty' is the definition.
('punishment' can be a synonym of 'penalty')
'kick is hard guys admitted' is the wordplay.
'kick' becomes 'punt' (punting is a kind of kicking**).
'hard' becomes 'h'.
'guys' becomes 'men'.
'admitted' indicates putting letters inside.
'is'+'h'+'men'='ishmen'
'punt' going around 'ishmen' is 'PUNISHMENT'.
(Other definitions for punishment that I've seen before include "That may be fine" , "Sanction" , "Discipline" , "See 6" , "Beating" .)