Frugal items parent is keeping (5)

I believe the answer is:

spare

'frugal' is the definition.
(thesaurus)

'items parent is keeping' is the wordplay.
'is keeping' indicates a hidden word.
'SPARE' can be found hidden inside 'items parent'.

(Other definitions for spare that I've seen before include "Free" , "not in actual use" , "Additional; thin" , "Additional - for use when needed" , "Leftover" .)

I've seen this clue in The Telegraph.

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