Breaking lock, step inside? (8)
I believe the answer is:
trespass
'breaking' is the definition.
(thesaurus)
'lock step inside?' is the wordplay.
'lock' becomes 'tress' (both can mean a piece of hair).
'step' becomes 'pas' (I've seen this in another clue).
'inside?' means one lot of letters goes inside another.
'tress' going around 'pas' is 'TRESPASS'.
(Other definitions for trespass that I've seen before include "Unlawful entry to someone's property" , "Sin (archaic)" , "Encroachment" , "Enter someone's property unlawfully" , "Transgress" .)