Year of good fortune displacing 50 of a disgusting nature (5)
I believe the answer is:
yucky
'of a disgusting nature' is the definition.
'year of good fortune displacing 50' is the wordplay.
'year' becomes 'y'.
'of good fortune' becomes 'lucky'.
'displacing' suggests deleting specific letters.
'50' becomes 'l' ('L' can be a synonym of '50').
'lucky' with 'l' removed is 'ucky'.
'y'+'ucky'='YUCKY'
(Other definitions for yucky that I've seen before include "Revolting" , "Messy, disgusting" .)