Slough has one trapped, progress hampered? (6,4)
I believe the answer is:
bogged down
'progress hampered?' is the definition.
(if you're bogged down, your progress is hampered)
'slough has one trapped' is the wordplay.
I cannot quite see how this works, but
'slough' could be 'bog' (both can mean a swampy area) and 'bog' is found within the answer.
'one' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for bogged down that I've seen before include "Literally or figuratively stuck in the mud" , "Encumbered with too much work" , "Overwhelmed" , "as a peat-cutter?" .)