Bond sprang up to speak (4)
I believe the answer is:
weld
'bond' is the definition.
(as in welding things together)
'sprang up to speak' is the wordplay.
'sprang up' becomes 'welled' (as in tears springing or welling).
'to speak' shows a homophone (sound like).
'welled' sounds like 'WELD'.
(Other definitions for weld that I've seen before include "Join together by heating" , "Metal-to-metal join" , "Unite metals by heating to melting point" , "Fuse metal parts" , "Join using fusion" .)