Quid secures a second nut (6)
I believe the answer is:
cashew
'nut' is the definition.
(cashew is a kind of nut)
'quid secures a second' is the wordplay.
'quid' becomes 'chew' ('chew' can be a synonym of 'quid'**).
'secures' means one lot of letters goes inside another.
'a second' becomes 'as' (I've seen this in other clues).
'chew' going around 'as' is 'CASHEW'.
(Other definitions for cashew that I've seen before include "nut-tree" , "Acajou" , "Kind of nut" , "Common type of nut" , "Chew as you would this nut" .)