Rest of spiders I trap at intervals (6)
I believe the answer is:
siesta
'rest' is the definition.
(I know that siesta is a type of nap)
'spiders i trap at intervals' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'spiders'+'i'+'trap'='spidersitrap'
The alternating letters of 'spidersitrap' are 'SIESTA'.
'of' acts as a link.
(Other definitions for siesta that I've seen before include "PM snoozing?" , "PM snooze" , "Afternoon relaxation" , "Afternoon nap in Cadiz" , "Catnap" .)