So reticent in altering meeting (12)
I believe the answer is:
intersection
'meeting' is the definition.
(thesaurus)
'so reticent in altering' is the wordplay.
'altering' indicates an anagram.
'so'+'reticent'+'in'='soreticentin'
'soreticentin' is an anagram of 'INTERSECTION'.
(Other definitions for intersection that I've seen before include "Motorway junction" , "Crossing point" , "Crossing - junction" , "Where two lines cross" .)