WW1 gun in comfortable position secured by a wedge from below (3,6)
I believe the answer is:
big bertha
'ww1 gun in comfortable' is the definition.
I can't judge whether this definition defines the answer.
'position secured by a wedge from below' is the wordplay.
'position' becomes 'berth' (synonyms).
'secured by' means one lot of letters goes inside another (inserted letters are held or secured).
'wedge' becomes 'gib'.
'from below' is a reversal indicator (in a down clue, letters go up).
'a'+'gib'='agib'
'agib' reversed gives 'biga'.
'berth' placed inside 'biga' is 'BIG BERTHA'.
Can you help me to learn more?
(Other definitions for big bertha that I've seen before include "WWI German siege gun" , "Great War German gun" , "cannon" .)