Squatter discovered in bed with lit match and brier (6,4)
I believe the answer is:
hermit crab
'squatter' is the definition.
(I have seen 'Marine squatter' mean 'hermit crab' so perhaps 'squatter' could also mean 'hermit crab')
'lit match and brier' is the wordplay.
'lit' is an anagram indicator (lit can mean drunk).
'and' means one lot of letters go next to another.
'match'+'brier'='matchbrier'
'matchbrier' anagrammed gives 'HERMIT-CRAB'.
'discovered in bed with' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for hermit crab that I've seen before include "Creature inhabiting empty shell of another" , "One wearing cast-offs" , "aquatic creature" , "Little creature with nippers" , "that goes on sidewalk?" .)