In haste, struggling with a muscular problem (8)
I believe the answer is:
asthenia
'muscular problem' is the definition.
The definition and answer can be both states of affairs as well as being singular nouns.
Maybe there's a link between them I don't understand?
'in haste struggling with a' is the wordplay.
'struggling with' indicates anagramming the letters (the letters struggle or wriggle into a new form).
'in'+'haste'='inhaste'
'inhaste' mixed up with 'a' makes 'ASTHENIA'.
Can you help me to learn more?
(Other definitions for asthenia that I've seen before include "loss of strength" , "Weakness" .)