Buffoons lowering the odds of seeing these? (4)
I believe the answer is:
'seeing these?' is the definition.
The definition suggests an adverb but the answer is not.
'buffoons lowering the odds' is the wordplay.
'lowering the odds' indicates alternate letters (letters in odd-numbered positions drop out).
The alternating letters of 'buffoons' are 'UFOS'.
'of' is the link.
(Other definitions for ufos that I've seen before include "Roswell sightings?" , "Potential alien craft" , "Initially and formally, flying saucers" , "Mysterious things" , "Initially, formal flying saucers" .)