Robbers appear the night before breaking into this (7)
I believe the answer is:
thieves
'robbers' is the definition.
(I've seen this before)
'night before breaking into this' is the wordplay.
'night before' becomes 'eve' (eve can mean the night before something).
'breaking into' is an insertion indicator.
'eve' placed inside 'this' is 'THIEVES'.
'appear the' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for thieves that I've seen before include "eg Pick-pockets" , "Stealers" , "Light-fingered people" , "Robbers" , "Pilferers" .)