Sister I left, somewhat lacking in creativity (7)

I believe the answer is:

sterile

'lacking in creativity' is the definition.
(sterile can mean uncreative or dull)

'sister i left somewhat' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'STERILE' can be found hidden inside 'sister i left'.

(Other definitions for sterile that I've seen before include "Pointless" , "like a mule" , "Lab so clean" , "Not able to produce offspring" , "Antiseptic" .)

I've seen this clue in The Telegraph.

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