Break into home, start to pilfer in small tower in reverse (9)
I believe the answer is:
interrupt
'break into' is the definition.
(I've seen this before)
'home start to pilfer in small tower in reverse' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'start to' says to take the initial letters.
'in' means one lot of letters goes inside another.
'small tower' becomes 'turret' (I've seen this before).
'in reverse' says the letters should be written backwards.
The first letter of 'pilfer' is 'p'.
'p' put within 'turret' is 'tpurret'.
'tpurret' in reverse letter order is 'terrupt'.
'in'+'terrupt'='INTERRUPT'
(Other definitions for interrupt that I've seen before include "Break the continuity of" , "middle of ashtray after burning slip gets put out" .)