Leaves oddly sick sheep (6)
I believe the answer is:
scrams
'leaves' is the definition.
(scramming is a kind of leaving)
'oddly sick sheep' is the wordplay.
'oddly' means one should take alternating letters.
'sheep' becomes 'rams' (I have seen 'Male sheep ' mean 'rams' so perhaps 'sheep' could also mean 'rams').
The alternate letters of 'sick' are 'sc'.
'sc'+'rams'='SCRAMS'
(Other definitions for scrams that I've seen before include "goes off, it's said" , "Suddenly leaves" , "Buzzes off, vamooses" .)