Safe time to probe member of The House of Lords (5)
I believe the answer is:
peter
'safe' is the definition.
(slang term for a safe)
'time to probe member of the house of lords' is the wordplay.
'time' becomes 't' (abbreviation).
'to probe' means one lot of letters goes inside another (probe can mean to poke or prod into).
'member of the house of lords' becomes 'peer' (I've seen this before).
't' going inside 'peer' is 'PETER'.
(Other definitions for peter that I've seen before include "Boy's name - safe" , "- Sellers, twentieth century English comedian" , "Rock-like apostle" , "Lord -- Wimsey (Sayers)" , "' - - Pan' by Barrie" .)