Regularly co-opt new dean close to busy time when the public may visit college? (4,3)
I believe the answer is:
open day
'time when the public may visit college?' is the definition.
'regularly co-opt new dean close to busy' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'new' indicates an anagram.
'close to' says to take the final letters (the close/ending of).
The last letter of 'busy' is 'y'.
'co'+'opt'='coopt'
The alternating letters of 'coopt' are 'op'.
'dean' is an anagram of 'enda'.
'op'+'enda'+'y'='OPEN DAY'
(Other definitions for open day that I've seen before include "Free access time" , "Dostoyevsky novel" , "Opportunity for public to visit" , "often held by institution" , "Time for public to visit" .)