Using broken straw, the Spanish spendthrift (7)
I believe the answer is:
wastrel
'spendthrift' is the definition.
(I've seen this in another clue)
'using broken straw the spanish' is the wordplay.
I cannot really see how this works, but
an anagram of 'straw' is 'wastr' which is located in the answer.
'the spanish' could be 'el' ('the' in Spanish) and 'el' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for wastrel that I've seen before include "Layabout" , "Person who dissipates resources self-indulgently" , "Prodigal" , "Ne'er-do-well" , "Useless person" .)