Bet political advisor will keep source of scandal in reserve (3,5)
I believe the answer is:
lay aside
'reserve' is the definition.
(I've seen this before)
'bet political advisor will keep source of scandal' is the wordplay.
'bet' becomes 'lay' (lay bet is a type of bet in gambling).
'political advisor' becomes 'aide' (I can't explain this - if you can you should believe this answer much more).
'will keep' indicates putting letters inside.
'source of' says to take the initial letters (the start - or source - of the word).
The initial letter of 'scandal' is 's'.
'aide' going around 's' is 'aside'.
'lay'+'aside'='LAY ASIDE'
'in' is the link.
Can you help me to learn more?
(Other definitions for lay aside that I've seen before include "give up!" , "Abandon - store for future" , "Discard - put by for future use" , "reserve" , "Abandon - save for later" .)