English town I document under Henry (7)
I believe the answer is:
halifax
'english town' is the definition.
(town in West Yorkshire)
'i document under henry' is the wordplay.
'document' becomes 'fax' (document sent with a fax machine).
'under' means one lot of letters go next to another.
'henry' becomes 'hal' (short for Henry).
'i'+'fax'='ifax'
'ifax' put after 'hal' is 'HALIFAX'.
(Other definitions for halifax that I've seen before include "Canadian port" , "Nova Scotia capital; Yorks. town" , "Minster town" , "Canadian city; Yorkshire town" , "somewhere in Canada" .)