Sappers said to go free (7)
I believe the answer is:
relieve
'go free' is the definition.
'relieve' can be an answer for 'free' (I've seen this in another clue). I am not certain of the 'go' bit.
'sappers said' is the wordplay.
'sappers' becomes 'RE' (nickname for the Royal Engineers).
'said' becomes 'lieve' (I can't explain this - if you can you should believe this answer much more).
're'+'lieve'='RELIEVE'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for relieve that I've seen before include "Alleviate 9pain)" , "help" , "Ease pain or burden" , "Release from duty" , "Alleviate pain or stress" .)