Founder lacking sparkle after trip (4,4)
I believe the answer is:
fall flat
'founder' is the definition.
(synonyms)
'lacking sparkle after trip' is the wordplay.
'lacking sparkle' becomes 'flat' (I've seen this before).
'after' says to put letters next to each other.
'trip' becomes 'fall' (fall is a kind of trip).
'flat' after 'fall' is 'FALL FLAT'.
(Other definitions for fall flat that I've seen before include "Fail to impress" , "what a bad crack will do" , "flounder" , "Fail to get result - topple horizontally" , "Fail completely to produce the intended effect" .)