Scotland's leader doesn't have trousers (6)
I believe the answer is:
slacks
'trousers' is the definition.
(type of trousers)
'scotland's leader doesn't have' is the wordplay.
'leader' suggests taking the first letters.
'doesn't have' becomes 'lacks' (lacking something means not having it).
The first letter of 'scotlands' is 's'.
's'+'lacks'='SLACKS'
(Other definitions for slacks that I've seen before include "takes it easy" , "casual attire" , "Works lazily; trousers" , "Loose casual trousers" , "bags" .)