Tablet's taken out of fatigue, showing caution (8)
I believe the answer is:
wariness
'showing caution' is the definition.
(being wary is showing caution)
'tablet's taken out of fatigue' is the wordplay.
'tablet' becomes 'e' (E can mean ecstasy or an ecstasy tablet).
'taken out of' suggests deleting specific letters.
'fatigue' becomes 'weariness' (feeling fatigued or weary).
'weariness' with 'e' removed is 'WARINESS'.
(Other definitions for wariness that I've seen before include "State of caution" , "Circumspection" , "Caution, watchfulnes" .)