Wagon ruined in middle of hole, mistake in ground (3,4)
I believe the answer is:
own goal
'mistake in ground' is the definition.
'own goal' can be an answer for 'mistake' (I've seen this before). I'm not sure about the 'in ground' bit.
'wagon ruined in middle of hole' is the wordplay.
'ruined' is an anagram indicator.
'in' indicates putting letters inside.
'middle of' indicates the central letters.
The middle of 'hole' is 'ol'.
'wagon' is an anagram of 'wngoa'.
'wngoa' placed into 'ol' is 'OWN GOAL'.
Can you help me to learn more?
(Other definitions for own goal that I've seen before include "or occasionally with it?" , "A score against one's self or team" , "Action taken which results in a disadvantage to the taker" , "Self-made disadvantage" , "aids the opposition" .)