The tops of eclairs frequently melt and spread out (6)
I believe the answer is:
effuse
'spread out' is the definition.
(effuse can mean to emit or spread)
'the tops of eclairs frequently melt' is the wordplay.
'the tops of' suggests taking the first letters.
'melt' becomes 'fuse' (fusing is a kind of melting).
The first letters of 'eclairs frequently' is 'ef'.
'ef'+'fuse'='EFFUSE'
'and' is the link.
(Other definitions for effuse that I've seen before include "Pour or spread out" , "Gush" , "Pour forth (words)" .)