Soldiers taking an attitude of rest (6)
I believe the answer is:
repose
'rest' is the definition.
('repose' can be a synonym of 'rest')
'soldiers taking an attitude' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'taking' says to put letters next to each other.
'an attitude' becomes 'pose' (I've seen this before**).
're'+'pose'='REPOSE'
'of' is the link.
(Other definitions for repose that I've seen before include "State of tranquillity" , "Relaxation" , "Quiet restfulness" , "peace" , "Lie at rest" .)