Fired up in fight for knife (8)
I believe the answer is:
stiletto
'knife' is the definition.
(stiletto is a kind of knife)
'fired up in fight' is the wordplay.
'fired' becomes 'lit' (set on fire).
'up' is a reversal indicator (in down clue: letters go upwards).
'in' indicates putting letters inside.
'fight' becomes 'setto' (set-to is a kind of fight**).
'lit' written backwards gives 'til'.
'til' going inside 'setto' is 'STILETTO'.
'for' is the link.
(Other definitions for stiletto that I've seen before include "Bedspread" , "Long dagger" , "A short knife, dagger or heel" , "High-heeled shoe" , "Long thin knife" .)