Soldiers with land vehicle -- soldiers to leave, pull back (7)
I believe the answer is:
retract
'pull back' is the definition.
(I know that pull back can be written as retract)
'soldiers with land vehicle soldiers to leave' is the wordplay.
'soldiers' becomes 'RE' (Royal Engineers).
'with' says to put letters next to each other.
'land vehicle' becomes 'tractor' (vehicle used on farmland).
'soldiers' becomes 'OR' (Other Ranks).
'to leave' is a deletion indicator.
'tractor' with 'or' removed is 'tract'.
're'+'tract'='RETRACT'
(Other definitions for retract that I've seen before include "Reverse" , "Take back what was said" , "Recant" , "Revoke" , "Withdraw (offer, statement etc)" .)