Losing case, The Yard cracked persistent problem (5)
I believe the answer is:
hydra
'problem' is the definition.
(I know that hydra is a type of problem)
'losing case the yard cracked persistent' is the wordplay.
I cannot really see how this works, but
an anagram of 'yard' is 'ydra' which is within the answer.
A single letter 'h' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hydra that I've seen before include "M any-headed monster fought by Hercules" , "Many-headed foe of Hercules" , "Mythological monster with nine heads" , "Many-headed serpent" , "Multi-headed monster killed by Hercules" .)