Health insurance partly insufficient (4)

I believe the answer is:

thin

'insufficient' is the definition.
(thesaurus)

'health insurance partly' is the wordplay.
'partly' indicates a hidden word.
'THIN' is hidden within 'health insurance'.

(Other definitions for thin that I've seen before include "Lean; make (plants) less crowded" , "Watered down" , "Fine" , "Having little width" , "Lacking substance; not dense" .)

I've seen this clue in The Times.

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