Agreement of new number during summer in France (7)
I believe the answer is:
entente
'agreement' is the definition.
(I've seen this before)
'new number during summer in france' is the wordplay.
'new' becomes 'n'.
'number' becomes 'ten' (ten is a kind of number).
'during' is an insertion indicator.
'summer in france' becomes 'ete' (').
'n'+'ten'='nten'
'nten' going into 'ete' is 'ENTENTE'.
'of' is the link.
(Other definitions for entente that I've seen before include "Harmony" , "A friendly understanding between countries, may be cordial" , "Friendly agreement between countries" , "Friendly alliance between states" , "Interstate understanding" .)