Just small and intimate (6)
I believe the answer is:
simply
'just' is the definition.
('simply' can be a synonym of 'just')
'small and intimate' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'and' says to put letters next to each other.
'intimate' becomes 'imply' (I've seen this before).
's'+'imply'='SIMPLY'
(Other definitions for simply that I've seen before include "Without fuss" , "In a straightforward manner" , "Merely, just" .)