Mental weariness leads suit astray (9)

I believe the answer is:

lassitude

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'mental weariness' is the definition.
'lassitude' can be an answer for 'weariness' (I've seen this before). I'm not certain of the 'mental' bit.

'leads suit astray' is the wordplay.
'astray' indicates an anagram.
'leads'+'suit'='leadssuit'
'leadssuit' is an anagram of 'LASSITUDE'.

Can you help me to learn more?

(Other definitions for lassitude that I've seen before include "Sluggishness" , "30 [LETHARGY]" , "Listlessness, lethargy" , "Listlessness, fatigue" , "Is saluted with tiredness" .)

I've seen this clue in The Independent.

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