Most reluctant to give positive response in bed (6)
I believe the answer is:
coyest
'most reluctant' is the definition.
(I've seen this before)
'positive response in bed' is the wordplay.
'positive response' becomes 'yes' (positive response to a question).
'in' is an insertion indicator.
'bed' becomes 'cot' (cot is a type of bed).
'yes' going into 'cot' is 'COYEST'.
'to give' is the link.
(Other definitions for coyest that I've seen before include "Most modest" , "Most reluctant" .)