Tiny particle could make one turn queasy (7)
I believe the answer is:
neutron
'tiny particle' is the definition.
'one turn queasy' is the wordplay.
'queasy' indicates anagramming the letters.
'one'+'turn'='oneturn'
'oneturn' is an anagram of 'NEUTRON'.
'could make' is the link.
(Other definitions for neutron that I've seen before include "Elementary particle with zero charge" , "one's not charged" , "Chargeless particle" , "one isn't charged" , "Uncharged subatomic particle" .)