Strong feeling of tiredness? (3)
I believe the answer is:
ire
'strong feeling' is the definition.
(I've seen this before)
'of tiredness' is the wordplay.
'of' says the answer is hidden in the clue.
'IRE' can be found hidden inside 'tiredness'.
(Other definitions for ire that I've seen before include "Strong feeling" , "Choler" , "Anger among admirers" , "Anger, rage" , "heat" .)