Informal trousers (6)
I believe the answer is:
slacks
'informal trousers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slacks that I've seen before include "Loose casual trousers" , "Things to wear" , "Avoids work - trousers" , "Pants for casual wear" , "bags" .)