Bill and I cutting rhubarb, showing skill (6)
I believe the answer is:
adroit
'skill' is the definition.
(I've seen this before)
'bill and i cutting rhubarb' is the wordplay.
'bill' becomes 'ad' (advertisement stuck on wall).
'and' means one lot of letters go next to another.
'cutting' is an insertion indicator (some letters cut their way into a word).
'rhubarb' becomes 'rot' (both can mean nonsense or false information).
'i' going inside 'rot' is 'roit'.
'ad'+'roit'='ADROIT'
'showing' acts as a link.
(Other definitions for adroit that I've seen before include "handy" , "Deft and proficient" , "Skilful or ingenious" , "Clever, skilful" , "To raid (anag)" .)