Corpulent guide, terribly weary (8)
I believe the answer is:
fatigued
'weary' is the definition.
(I've seen this before)
'corpulent guide terribly' is the wordplay.
'corpulent' becomes 'fat' ('fat' can be similar in meaning to 'corpulent').
'terribly' indicates an anagram.
'guide' with letters rearranged gives 'igued'.
'fat'+'igued'='FATIGUED'
(Other definitions for fatigued that I've seen before include "Extremely tired" , "Drained of energy" , "Tired, really weary" , "needing the rest" , "Exhausted" .)