Soldiers pull back to observe (6)
I believe the answer is:
regard
'observe' is the definition.
(thesaurus)
'soldiers pull back' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'pull' becomes 'drag' (drag is a kind of pull**).
'back' says the letters should be written backwards.
'drag' written backwards gives 'gard'.
're'+'gard'='REGARD'
'to' acts as a link.
(Other definitions for regard that I've seen before include "Look at - estimation" , "Look at - esteem" , "Attention; esteem" , "Attitude of admiration or esteem" , "Consideration" .)