Generals start to vary wildly? Sauce! (5)
I believe the answer is:
gravy
'sauce' is the definition.
(gravy is a kind of sauce)
'generals start to vary wildly?' is the wordplay.
'start to' suggests taking the first letters.
'wildly?' indicates an anagram (I've seen 'wildly' mean this).
The initial letter of 'generals' is 'g'.
'vary' anagrammed gives 'ravy'.
'g'+'ravy'='GRAVY'
(Other definitions for gravy that I've seen before include "Meat jus" , "Sauce from meat juice" , "something saucy" , "contents of boat or train" , "Meat juices after cooking" .)