Stand in line on centre ground (7)
I believe the answer is:
lectern
'stand' is the definition.
(I know that lectern is a type of stand)
'line on centre ground' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'on' means one lot of letters goes inside another.
'ground' indicates an anagram ('grind' the letters into a new form).
'centre' is an anagram of 'ectern'.
'l' inserted inside 'ectern' is 'LECTERN'.
'in' is the link.
(Other definitions for lectern that I've seen before include "Speaker's stand" , "Bible stand" , "Support for bible in church" , "speaker's position" , "Slanted stand for a book" .)