Escort again joins one going back East (7)
I believe the answer is:
retinue
'escort' is the definition.
(thesaurus)
'again joins one going back east' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'joins' means one lot of letters go next to another.
'one' becomes 'unit' (synonyms).
'going back' is a reversal indicator.
'east' becomes 'e' (synonyms).
'unit' back-to-front is 'tinu'.
're'+'tinu'+'e'='RETINUE'
(Other definitions for retinue that I've seen before include "Group attending a person" , "Train, following" , "Entourage, followers" , "Group of followers" , "Suite of followers" .)