Cleaners, underworked, having coffee outside (10)
I believe the answer is:
laundrette
'cleaners' is the definition.
(establishment where clothes can be cleaned)
I don't understand how the remainder of the clue works.
(Other definitions for laundrette that I've seen before include "Wash-room" , "Washing establishment" , "On film, mine was beautiful" , "cleaning outfit" .)