Secure most of the layer (3)
I believe the answer is:
tie
'secure' is the definition.
(I've seen this before)
'most of the layer' is the wordplay.
'most of' means to remove the last letter.
'the layer' becomes 'tier' (tier is a kind of layer).
'tier' with its last letter taken away is 'TIE'.
(Other definitions for tie that I've seen before include "Attach, fasten" , "restraint" , "Fasten; draw" , "item round neck" , "Bind; knot" .)