Affectedly dainty — as in "The Go-Between" (4)
I believe the answer is:
twee
'affectedly dainty' is the definition.
(I've seen this before)
'in the go-between' is the wordplay.
'in' indicates a hidden word.
'TWEE' is hidden within 'go between'.
'as' acts as a link.
(Other definitions for twee that I've seen before include "Small and sweet (colloq.)" , "Affected quaint" , "Over-pretty, sentimental" , "Small and pretty" , "Sentimentally sweet" .)