Spades have to be put in soil (4)
I believe the answer is:
sown
'to be put in soil' is the definition.
I can't judge whether this definition defines the answer.
'spades have' is the wordplay.
'spades' becomes 's' (abbreviation in card games).
'have' becomes 'own' (to have something is to own it).
's'+'own'='SOWN'
Can you help me to learn more?
(Other definitions for sown that I've seen before include "(Of seeds) planted" , "Broadcast" , "(Of seed) planted" , "set out to grow" , "Placed in ground as seed" .)