Left spade out, no longer valid (6)
I believe the answer is:
lapsed
'no longer valid' is the definition.
I can't judge whether this definition defines the answer.
'left spade out' is the wordplay.
'left' becomes 'l' (common abbreviation).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'spade' anagrammed gives 'apsed'.
'l'+'apsed'='LAPSED'
Can you help me to learn more?
(Other definitions for lapsed that I've seen before include "Expired over pedals" , "Became void through disuse" , "Pleads (anag)" , "Ceased to practise faith" , "Pleads, having failed to maintain standards" .)