New service linking termini in Europe together (2,5)
I believe the answer is:
en masse
'together' is the definition.
(French phrase meaning all together)
'new service linking termini in europe' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'service' becomes 'mass' (church service).
'linking' is an insertion indicator (the inserted material links two sets of letters).
'termini in europe' becomes 'ee' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'n'+'mass'='nmass'
'nmass' inserted into 'ee' is 'EN MASSE'.
Can you help me to learn more?
(Other definitions for en masse that I've seen before include "in concert" , "Sees man (anag.)" , "As a body (Fr.)" , "as a bunch" , "Many as one" .)