Short rest, or rather be active? (8)
I believe the answer is:
breather
'short rest' is the definition.
(I've seen this in another clue)
'rather be active?' is the wordplay.
'active?' is an anagram indicator (I've seen 'active' mean this (the letters are active/moving)).
'rather'+'be'='ratherbe'
'ratherbe' anagrammed gives 'BREATHER'.
'or' acts as a link.
(Other definitions for breather that I've seen before include "Informally a pause for rest - or to take in air" , "Brief pause for rest" , "Short pause for rest" , "Recovery time" , "One's probably not dying" .)