Initially, Fawkes in anger causes disarray (5)
I believe the answer is:
rifle
'disarray' is the definition.
(I've seen this before)
'initially fawkes in anger' is the wordplay.
'initially' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'anger' becomes 'rile' (rile can mean to annoy or anger).
The first letter of 'fawkes' is 'f'.
'f' placed into 'rile' is 'RIFLE'.
'causes' acts as a link.
(Other definitions for rifle that I've seen before include "Search and rob - with long gun?" , "Winchester" , "Go through in search" , "Gun; sack" , "Long-barrelled weapon, normal army equipment" .)