Deals suit out in weariness (9)
I believe the answer is:
lassitude
'weariness' is the definition.
(I've seen this before)
'deals suit out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'deals'+'suit'='dealssuit'
'dealssuit' with letters rearranged gives 'LASSITUDE'.
'in' acts as a link.
(Other definitions for lassitude that I've seen before include "slackness" , "Lack of energy and enthusiasm" , "Weakness" , "Sluggishness" , "30 [LETHARGY]" .)