Dug under half of shed producing tremor (7)
I believe the answer is:
shudder
'tremor' is the definition.
(shuddering is a kind of tremoring)
'dug under half of shed' is the wordplay.
'dug' becomes 'udder' (I can't justify this - if you can you should give a lot more credence to this answer).
'under' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'half of' suggests halving the letters.
'shed' halved is 'sh'.
'udder' after 'sh' is 'SHUDDER'.
'producing' is the link.
Can you help me to learn more?
(Other definitions for shudder that I've seen before include "Shiver in fear or revulsion" , "Convulse" , "Shake with fear" , "Shiver with horror" , "Tremble through fear" .)