Man in pub falls over? This clearly hasn't worked (5)
I believe the answer is:
rehab
'this clearly hasn't worked' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'man in pub falls over?' is the wordplay.
'man' becomes 'ab'.
'in pub falls' becomes 'reh' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'over?' says to put letters next to each other.
'ab' after 'reh' is 'REHAB'.
(Other definitions for rehab that I've seen before include "Health-restoring process" , "Treatment for alcohol abuse" , "Place to go, in short, to be restored to fitness" , "Treatment for, eg, addiction" , "remedial treatment" .)