Spirit level in a mine brought to one working (10)
I believe the answer is:
apparition
'spirit' is the definition.
(I know that apparition is a type of spirit)
'level in a mine brought to one working' is the wordplay.
'level' becomes 'par' (average level on a golf course).
'in' indicates putting letters inside.
'mine' becomes 'pit' (down the pit).
'brought to' says to put letters next to each other.
'one working' becomes 'ion' (I can't justify this - if you can you should believe this answer much more).
'a'+'pit'='apit'
'par' going into 'apit' is 'apparit'.
'apparit'+'ion'='APPARITION'
(Another definition for apparition that I've seen is " Ghost".)