Escort across to assume control (4,4)
I believe the answer is:
take over
'assume control' is the definition.
(I've seen this before)
'escort across' is the wordplay.
'escort' becomes 'take' (both can mean to guide or accompany someone).
'across' becomes 'over' (synonyms).
'take'+'over'='TAKE-OVER'
'to' acts as a link.
(Other definitions for take over that I've seen before include "This bid is for control of a business" , "Assume control of" , "Act of assuming control" , "Company buyout" , "Buying out of one company by another" .)