Seminars replaced meeting thankfully avoided (4,4)
I believe the answer is:
near miss
'meeting thankfully avoided' is the definition.
(I've seen this before)
'seminars replaced' is the wordplay.
'replaced' indicates anagramming the letters.
'seminars' anagrammed gives 'NEAR MISS'.
(Other definitions for near miss that I've seen before include "Just off the target (4,4)" , "Almost a hit" , "Failure just" , "Close call" , "almost getting killed?" .)