Crawl as cops seen in room (6,4)
I believe the answer is:
snails pace
'crawl' is the definition.
(both can mean a very slow pace)
'cops seen in room' is the wordplay.
'cops' becomes 'nails' ('nail' can be a synonym of 'cop').
'seen in' means one lot of letters goes inside another.
'room' becomes 'space' (I've seen this before).
'nails' inserted within 'space' is 'SNAILS PACE'.
'as' is the link.
(Other definitions for snails pace that I've seen before include "making slow progress" , "no rush" , "Very slow speed" , "at a very low rate" , "Slow rate of progress" .)