Life peer's concealed weapon (4)
I believe the answer is:
epee
'weapon' is the definition.
(epee is a kind of weapon)
'life peer's concealed' is the wordplay.
'concealed' says the answer is hidden in the clue.
'EPEE' can be found hidden inside 'life peers'.
(Other definitions for epee that I've seen before include "Use it to fence" , "there's a point to it" , "It may offer riposte" , "Another fencing sword" , "sports equipment" .)