Insubstantial desire; possibly say why (5-5)

I believe the answer is:

wishy-washy

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'insubstantial' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I don't see?

'desire possibly say why' is the wordplay.
'desire' becomes 'wish' (wish is a kind of desire).
'possibly' indicates anagramming the letters.
'say'+'why'='saywhy'
'saywhy' with letters rearranged gives 'ywashy'.
'wish'+'ywashy'='WISHY-WASHY'

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(Other definitions for wishy-washy that I've seen before include "Feeble, insipid" , "Watered-down" , "Bland -- pale" , "Ineffectual" , "Diluted" .)

I've seen this clue in The Globe and Mail.

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