Call me in on mishandled meeting about ... (10)
I believe the answer is:
denominate
'call' is the definition.
(thesaurus)
'me in on mishandled meeting about' is the wordplay.
'mishandled' indicates anagramming the letters.
'meeting' becomes 'date' (date is a kind of meeting**).
'about' indicates putting letters inside.
'me'+'in'+'on'='meinon'
'meinon' with letters rearranged gives 'enomin'.
'enomin' placed inside 'date' is 'DENOMINATE'.
(Other definitions for denominate that I've seen before include "call" , "name" .)