Head for crowded raucous square where ecstasy's to be had? (5,4)
I believe the answer is:
cloud nine
'where ecstasy's to be had?' is the definition.
(someone on cloud nine is very happy)
'head for crowded raucous square' is the wordplay.
'head for' suggests taking the first letters.
'raucous' becomes 'loud' (I've seen this in another clue).
'square' becomes 'nine' (nine is a square number).
The first letter of 'crowded' is 'c'.
'c'+'loud'+'nine'='CLOUD-NINE'
(Other definitions for cloud nine that I've seen before include "Situation of great elation" , "On which one is blissfully happy" , "If you're on this, you're extremely happy" , "On this, one is extremely happy" .)