Old fencing American's taken out for scrap (3)
I believe the answer is:
jot
'scrap' is the definition.
(I've seen this before)
'old fencing american's taken out' is the wordplay.
'old fencing' becomes 'joust' (medieval sport similar to fencing).
'american' becomes 'US' (United States).
'taken out' indicates named letters should be taken away.
'joust' with 'us' taken out is 'JOT'.
'for' acts as a link.
(Other definitions for jot that I've seen before include "Write hurriedly" , "Small piece - note" , "Scrap" , "Set down briefly" , "Write a short note" .)