American giving no backing to Knight (4)
I believe the answer is:
yank
'american' is the definition.
(Yank is an example)
'giving no backing to knight' is the wordplay.
'giving' means one lot of letters go next to another.
'no' becomes 'nay' (I've seen this before).
'backing' says the letters should be written backwards.
'to knight' becomes 'k'.
'nay' in reverse letter order is 'yan'.
'yan' put next to 'k' is 'YANK'.
(Other definitions for yank that I've seen before include "Sharp tug" , "pluck" , "American native" , "sudden 24D [DRAW] ?" , "Countryman" .)