Rickety seat is used for afternoon nap (6)
I believe the answer is:
siesta
'for afternoon nap' is the definition.
(I've seen this before)
'rickety seat is' is the wordplay.
'rickety' indicates an anagram.
'seat'+'is'='seatis'
'seatis' is an anagram of 'SIESTA'.
'used' is the link.
(Other definitions for siesta that I've seen before include "Afternoon break" , "Seat is found for a Spanish rest period" , "PM snoozing?" , "rest of the Spaniards" , "Diurnal nap in Spain" .)