Crossing East, old spy changes stations (7)
I believe the answer is:
deploys
'stations' is the definition.
(to deploy someone is to station them somewhere)
'crossing east old spy changes' is the wordplay.
'crossing' means one lot of letters goes inside another (to cross can mean to go over or around).
'east' becomes 'e' (synonyms).
'changes' indicates an anagram.
'old'+'spy'='oldspy'
'oldspy' is an anagram of 'dploys'.
'e' put inside 'dploys' is 'DEPLOYS'.
(Other definitions for deploys that I've seen before include "Distributes strategically" , "Spreads out in position ready for battle" , "Moves into position for military action" .)