Called in a group of soldiers to plan (7)
I believe the answer is:
arrange
'plan' is the definition.
(I've seen this before)
'called in a group of soldiers' is the wordplay.
'called' becomes 'rang' (called on the phone).
'in' is an insertion indicator.
'group of soldiers' becomes 'RE' (abbreviation for Royal Engineers).
'a'+'re'='are'
'rang' going inside 'are' is 'ARRANGE'.
'to' acts as a link.
(Other definitions for arrange that I've seen before include "Put into a proper order" , "Put in order; make plans" , "Dispose" , "Put in order - organise" , "Set in order" .)