To disturb the rest before you go, is an offence (8)
I believe the answer is:
trespass
'an offence' is the definition.
(I've seen this before)
'to disturb the rest before you go' is the wordplay.
'to disturb' is an anagram indicator (I've seen 'disturbed' mean this (the order of letters is disturbed)).
'before' is a charade indicator (letters next to each other).
'you go' becomes 'pass' (I can't justify this - if you can you should give a lot more credence to this answer).
'rest' is an anagram of 'tres'.
'tres'+'pass'='TRESPASS'
'is' is the link.
Can you help me to learn more?
(Other definitions for trespass that I've seen before include "Enter another's property unlawfully" , "Invade" , "Unlawful entry to someone's property" , "Commit a sin -- spa's rest (anag)" , "Wrongfully enter another's land" .)