Depressions are closely compacted, it’s said (5)
I believe the answer is:
dents
'depressions' is the definition.
(dent is a kind of depression)
'closely compacted it's said' is the wordplay.
'closely compacted' becomes 'dense' (I've seen this before).
'it's said' indicates a 'sounds like' (homophone) clue.
'dense' is a homophone of 'DENTS'.
'are' is the link.
(Other definitions for dents that I've seen before include "reductions in size" , "Tends towards small depressions" , "Tends to create small depressions" , "Tends towards small depression" .)