Host seems clever occasionally (5)
I believe the answer is:
emcee
'host' is the definition.
(I know that host can be written as emcee)
'seems clever occasionally' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'seems'+'clever'='seemsclever'
The alternating letters of 'seemsclever' are 'EMCEE'.
(Other definitions for emcee that I've seen before include "Show host" , "show director" , "Master of ceremonies (mainly US)" , "A host of Americans" , "One presents" .)