In retrospect, General Trebonius gutted to produce blade (5)
I believe the answer is:
steel
'blade' is the definition.
(I know that blade can be written as steel)
'in retrospect general trebonius gutted' is the wordplay.
'in retrospect' says the letters should be written in reverse (in retrospect means looking back).
'general' becomes 'Lee' (Robert E. Lee - US revolutionary commander).
'gutted' suggests removing the centre (to gut something is to remove its insides).
'trebonius' with its middle taken out is 'ts'.
'lee'+'ts'='leets'
'leets' written backwards gives 'STEEL'.
'to produce' acts as a link.
(Other definitions for steel that I've seen before include "Mixture of carbon and iron" , "May be cold" , "The staying power" , "nerve" , "Determination, metal" .)