Pants but isn't exerting oneself (6)
I believe the answer is:
slacks
'pants' is the definition.
(slacks is a kind of pants)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for slacks that I've seen before include "bags" , "Works lazily; trousers" , "casual attire" , "Avoids work - trousers" , "Pants for casual wear" .)