Such lids can save cracking nuts (4)
I believe the answer is:
skid
'save cracking nuts' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'such lids can' is the wordplay.
'lids' indicates taking the first letters (I've seen 'lid' mean this (the top, or first, letter)).
'can' becomes 'kid' (I can't explain this - if you can you should give a lot more credence to this answer).
The initial letter of 'such' is 's'.
's'+'kid'='SKID'
Can you help me to learn more?
(Other definitions for skid that I've seen before include "Slip out of control" , "What car may do on ice - be careful" , "Slide (on slippery ground)" , "Slide fast" , "lose control momentarily" .)