One who steals £1 (6)
I believe the answer is:
nicker
'one who steals' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for nicker that I've seen before include "One stealing" , "thief" , "Sound made by horse" , "One steals" , "Money" .)