Photograph of gunners surrounded by axes (1-3)
I believe the answer is:
x-ray
'photograph' is the definition.
(I know that x-ray is a kind of photograph)
'gunners surrounded by axes' is the wordplay.
'gunners' becomes 'RA' (Royal Artillery).
'surrounded by' means one lot of letters goes inside another.
'axes' becomes 'xy' (x axis and y axis).
'ra' put inside 'xy' is 'X-RAY'.
'of' acts as a link.
(Other definitions for x-ray that I've seen before include "Hospital photograph" , "See-through photo" , "Picture used in medical diagnosis" , "Radiation photograph" , "Electromagnetic photograph" .)