Frame held by stake, securing device (7)
I believe the answer is:
bracket
'device' is the definition.
(I know that bracket is a type of device)
'frame held by stake' is the wordplay.
'frame' becomes 'rack' (rack is a kind of frame).
'held by' is an insertion indicator.
'stake' becomes 'bet' (synonyms).
'rack' placed within 'bet' is 'BRACKET'.
'securing' acts as a link.
(Other definitions for bracket that I've seen before include "L-shaped shelf support" , "Group together" , "Supporter" , "L-shaped support - one of a pair enclosing text" , "Parenthesis" .)