English label put back at the opening (4)
I believe the answer is:
gate
'the opening' is the definition.
(a gate is an opening or entrance)
'english label put back' is the wordplay.
'english' becomes 'E' (abbreviation).
'label' becomes 'tag' (synonyms).
'put back' says the letters should be written in reverse.
'e'+'tag'='etag'
'etag' in reverse letter order is 'GATE'.
'at' is the link.
(Other definitions for gate that I've seen before include "Field entrance" , "Barrier, exit" , "Entry barrier as to field" , "Access here" , "Attendance figure" .)