Saying concealed by Dermot today (5)
I believe the answer is:
motto
'saying' is the definition.
(I know that motto is a type of saying)
'concealed by dermot today' is the wordplay.
'concealed by' indicates the answer is hidden within the clue.
'MOTTO' can be found hidden inside 'dermot today'.
(Other definitions for motto that I've seen before include "Saying in a cracker" , "Brief guiding rule" , "It may be proverbial" , "Christmas cracker item" , "Cracker slip" .)