Get back with protection by Royal Engineers (7)
I believe the answer is:
recover
'get back' is the definition.
(I've seen this before)
'protection by royal engineers' is the wordplay.
'protection' becomes 'cover' (something that protects or shields).
'by' means one lot of letters go next to another.
'royal engineers' becomes 'RE' (abbreviation).
'cover' put after 're' is 'RECOVER'.
'with' is the link.
(Other definitions for recover that I've seen before include "comeback" , "Find" , "Get better - get back" , "Rescue" , "Obtain the return of" .)