Central part of idea by deputy for contrivance (6)
I believe the answer is:
device
'for contrivance' is the definition.
(I've seen this before)
'central part of idea by deputy' is the wordplay.
'central part of' indicates the central letters.
'by' means one lot of letters go next to another.
'deputy' becomes 'vice' (as in vice-president).
The middle of 'idea' is 'de'.
'de'+'vice'='DEVICE'
(Other definitions for device that I've seen before include "Contrivance; motto" , "Something made for a particular purpose" , "Mechanism, trick" , "Instrument made for a special purpose" , "Trick; heraldic design" .)