They dig pit in seconds (7)
I believe the answer is:
shovels
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps there's an association between them I don't understand?
'dig pit in seconds' is the wordplay.
'dig pit' becomes 'hovel' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'seconds' becomes 'ss' (an abbreviation for seconds written twice).
'hovel' placed inside 'ss' is 'SHOVELS'.
Can you help me to learn more?
(Other definitions for shovels that I've seen before include "Diggers" , "Implements" , "Spades" .)