Nick loses head in the sack - that's messed up (7)
I believe the answer is:
'messed up' is the definition.
('botch' can be a synonym of 'mess up')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for botched that I've seen before include "Messed up" , "Made a bags of" , "Made a mess of, spoiled by clumsy work" .)