Wedding participants carrying grand crosses (7)
I believe the answer is:
bridges
'crosses' is the definition.
(bridging is a kind of crossing)
'wedding participants carrying grand' is the wordplay.
'wedding participants' becomes 'brides' (women getting married).
'carrying' is an insertion indicator.
'grand' becomes 'g' (G is short for grand as in a thousand).
'brides' enclosing 'g' is 'BRIDGES'.
(Other definitions for bridges that I've seen before include "One responsible for lyrics" , "Spans" , "links" , "Robert -, poet laureate" , "WRITER" .)