Unhappy tale about pixie going back for flier (7)
I believe the answer is:
leaflet
'flier' is the definition.
(thesaurus)
'unhappy tale about pixie going back' is the wordplay.
'unhappy' indicates an anagram.
'about' means one lot of letters goes inside another.
'pixie' becomes 'elf' ('elf' can be a synonym of 'pixie').
'going back' is a reversal indicator.
'elf' in reverse letter order is 'fle'.
'tale' is an anagram of 'leat'.
'leat' placed around 'fle' is 'LEAFLET'.
'for' is the link.
(Other definitions for leaflet that I've seen before include "A pamphlet giving information" , "Small information sheet" , "Publication on single sheet" , "Small pamphlet" , "Distribute information" .)