Burst of French welcome — that is, when meeting English (7)
I believe the answer is:
dehisce
'burst' is the definition.
(dehisce means to burst open)
'of french welcome that is when meeting english' is the wordplay.
'of french' becomes 'de' ('of' in French).
'welcome' becomes 'hi' (both can be used as a greeting).
'that is' becomes 'sc' (abbrv. for Latin scilicet; 'namely').
'when meeting' means one lot of letters go next to another.
'english' becomes 'e' (abbreviation).
'de'+'hi'+'sc'+'e'='DEHISCE'
(Other definitions for dehisce that I've seen before include "Burst open, ejecting seeds" , "Gape" , "Seeds burst from pod" , "rupture" .)