Notorious ex-convict managed to enter empty flat (8)
I believe the answer is:
flagrant
'notorious' is the definition.
(I've seen this before)
'ex-convict managed to enter empty flat' is the wordplay.
'ex-convict' becomes 'lag' (I've seen this before).
'managed' becomes 'ran' (I've seen this in another clue).
'to enter' indicates putting letters inside.
'empty' says to hollow out the word (remove centre letters).
'flat' with its middle taken out is 'ft'.
'lag'+'ran'='lagran'
'lagran' placed into 'ft' is 'FLAGRANT'.
(Other definitions for flagrant that I've seen before include "Shocking" , "Patent" , "Being shameless" , "Barefaced" , "'Conspicuous, glaring (8)'" .)