Leave Ben without sentimental liaison (2-7)
I believe the answer is:
go-between
'liaison' is the definition.
(I've seen this before)
'leave ben without sentimental' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'sentimental' becomes 'twee' (I've seen this before).
'ben' going around 'twee' is 'between'.
'go'+'between'='GO-BETWEEN'
(Other definitions for go-between that I've seen before include "Runner" , "Intermediary" , "One who acts as messenger or negotiator" .)