Talks of having one infiltrate the thieves (7)
I believe the answer is:
pirates
'the thieves' is the definition.
(I know this)
'talks of having one infiltrate' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'talks' could be 'prates' (prating is a kind of talking) and 'prates' is found within the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pirates that I've seen before include "Bad sailors" , "Buccaneers" , "Robbers at sea" , "Chatters, talks foolishly" , "Robbers on the high seas" .)