Being terribly tired, Leo dawdled (8)
I believe the answer is:
loitered
'dawdled' is the definition.
(I've seen this before)
'being terribly tired leo' is the wordplay.
'being terribly' is an anagram indicator.
'tired'+'leo'='tiredleo'
'tiredleo' is an anagram of 'LOITERED'.
(Other definitions for loitered that I've seen before include "dilly-dallied" , "Stood about idly" , "Kicked heels" , "Stood around aimlessly" , "Hung around idly, dawdled" .)