As well as to footwear? (2,4)
I believe the answer is:
to boot
'as well' is the definition.
(I've seen this before)
'to footwear?' is the wordplay.
'footwear?' becomes 'boot' (boot is a kind of footwear).
'to'+'boot'='TO BOOT'
'as' is the link.
(Other definitions for to boot that I've seen before include "furthermore" , "What's more" , "Where an extra case may be added" , "Into the bargain" , "Moreover, in addition to (2,4)" .)