Peculiarity in icy dairy, sons recollected (12)
I believe the answer is:
idiosyncrasy
'peculiarity' is the definition.
(idiosyncrasy is a kind of peculiarity)
'icy dairy sons recollected' is the wordplay.
'recollected' indicates anagramming the letters.
'icy'+'dairy'+'sons'='icydairysons'
'icydairysons' with letters rearranged gives 'IDIOSYNCRASY'.
'in' is the link.
(Other definitions for idiosyncrasy that I've seen before include "Peculiarity" , "Foible" , "Oddity" , "Quirk" , "Distinctive mannerism" .)