Engineer eats last of canteen pap (7)
I believe the answer is:
snapper
'pap' is the definition.
(member of the paparazzi, someone who snaps photos)
'engineer eats last of canteen' is the wordplay.
'engineer' becomes 'sapper' (sapper is a kind of engineer).
'eats' indicates putting letters inside.
'last of canteen' becomes 'n' (I can't justify this - if you can you should give a lot more credence to this answer).
'sapper' placed around 'n' is 'SNAPPER'.
Can you help me to learn more?
(Other definitions for snapper that I've seen before include "(Often red) food fish" , "Person photographing" , "Fish; marine turtle" , "sharp-toothed fish" , "Fish; photographer" .)