Uniform available as quickly as possible (4,3)
I believe the answer is:
flat out
'as quickly as possible' is the definition.
(as in working flat out)
'uniform available' is the wordplay.
'uniform' becomes 'flat' (I've seen this in other clues).
'available' becomes 'out' (as in a product which is out).
'flat'+'out'='FLAT OUT'
(Other definitions for flat out that I've seen before include "As fast as possible" , "Lying on floor" , "At top speed - totally exhausted" , "Exhausted - at full speed" , "At top speed; intense (effort)" .)