Back of mining engineer nearer to dynamo (9)
I believe the answer is:
generator
'dynamo' is the definition.
(thesaurus)
'back of mining engineer nearer to' is the wordplay.
'back of' indicates one should take the final letters.
'engineer' indicates anagramming the letters.
The final letter of 'mining' is 'g'.
'nearer'+'to'='nearerto'
'nearerto' anagrammed gives 'enerator'.
'g'+'enerator'='GENERATOR'
(Other definitions for generator that I've seen before include "Engine to produce electricity" , "Power source" , "Eg, dynamo" , "It gives power" , "meant to be electrifying?" .)