Suave UCL man periodically appearing in a flap (5)
I believe the answer is:
uvula
'a flap' is the definition.
(I know that uvula is a type of flap)
'suave ucl man periodically appearing' is the wordplay.
'periodically appearing' indicates alternate letters (letters taken at regular or periodic intervals).
'suave'+'ucl'+'man'='suaveuclman'
The alternating letters of 'suaveuclman' are 'UVULA'.
'in' acts as a link.
(Other definitions for uvula that I've seen before include "Fleshy piece hanging over the throat" , "Part of one's mouth" , "Flap hanging in back of throat" , "Fleshy projection hanging from roof of mouth" , "Fleshy lobe" .)