Desire to meet small and sexy outsider (4,4)
I believe the answer is:
long shot
'outsider' is the definition.
(I've seen this before)
'desire to meet small and sexy' is the wordplay.
'desire' becomes 'long' (longing is a kind of desiring).
'to meet' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
'and' means one lot of letters go next to another.
'sexy' becomes 'hot' (similar in meaning).
'long'+'s'+'hot'='LONG SHOT'
(Other definitions for long shot that I've seen before include "Attempt at goal from half-way line" , "An attempt unlikely to be successful" , "A bet on outsider" , "An undertaking with little chance of success" , "What has little possibility of happening" .)