Part of dynamo under barrow (5)
I believe the answer is:
mound
'barrow' is the definition.
(thesaurus)
'part of dynamo under' is the wordplay.
'part of' says the answer is hidden in the clue.
'MOUND' can be found hidden inside 'dynamo under'.
(Other definitions for mound that I've seen before include "Earth bank" , "Raised mass of earth" , "Hillock; gold ball (Her.)" , "Mass of piled-up earth or stones" , "Heap (of raised earth)" .)