People kept inside houses pull up those making slow progress (8)
I believe the answer is:
laggards
'people' is the definition.
(laggard is a kind of person)
'slow progress' is the wordplay.
'slow' becomes 'laggard' (similar in meaning).
'progress' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'laggard'+'s'='LAGGARDS'
'kept inside houses pull up those making' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for laggards that I've seen before include "They make slow progress and fall behind others" , "Dawdlers" , "They tend to fall behind" , "Slow people; glad rags (anag.)" .)