Question European in Ritz waving gun (8)
I believe the answer is:
howitzer
'gun' is the definition.
(howitzer is a kind of gun)
'question european in ritz waving' is the wordplay.
'question' becomes 'how' (how is a question word).
'european' becomes 'e' (abbreviation e.g. EU).
'in' is an insertion indicator.
'waving' indicates anagramming the letters (letters wave around).
'ritz' anagrammed gives 'itzr'.
'e' placed into 'itzr' is 'itzer'.
'how'+'itzer'='HOWITZER'
(Other definitions for howitzer that I've seen before include "Gun for shelling" , "Killer" , "Short-range cannon" , "Gun firing shells at a steep angle" , "Type of gun" .)