Gather hoodlum accepts rule for where to let sleeping dogs lie (9)
I believe the answer is:
hearthrug
'where to let sleeping dogs lie' is the definition.
(dogs may lie on a rug by the fire)
'gather hoodlum accepts rule' is the wordplay.
'gather' becomes 'hear'.
'hoodlum' becomes 'thug' (synonyms).
'accepts' is an insertion indicator.
'rule' becomes 'r' (legal abbreviation).
'thug' enclosing 'r' is 'thrug'.
'hear'+'thrug'='HEARTHRUG'
'for' is the link.
(Other definitions for hearthrug that I've seen before include "one's position's under fire" , "One floored by blaze" , "Carpet in front of fire" , "floor-covering" , "Carpet by fireplace" .)