Poor girl's obsession? (5)

I believe the answer is:

thing

'obsession?' is the definition.
(I've seen this in other clues)

'poor girl's' is the wordplay.
'poor' becomes 'thin' (I've seen this in other clues).
'girl' becomes 'g'.
'thin'+'g'='THING'

(Other definitions for thing that I've seen before include "Object; gadget" , "Obsession" , "Individual unit" , "A creature" , "Article" .)

I've seen this clue in The Guardian.

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