To get thanks for fifty quid seems very unlikely (4)
I believe the answer is:
tall
'unlikely' is the definition.
(as in a tall tale)
'to get thanks for fifty quid seems very' is the wordplay.
I cannot really understand how this works, but
'thanks' could be 'ta' (UK informal version of 'thank you') and 'ta' is present in the answer.
'fifty' could be 'l' (Roman numeral) and 'l' is found in the answer.
A single letter 'l' 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 tall that I've seen before include "Towering" , "High in stature" , "Higher than the average person" , "Like giants" , "description of a giraffe?" .)