They have parallels, giving thanks when receiving a prize in error (8)
I believe the answer is:
trapezia
'they have parallels' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'thanks when receiving a prize in error' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'when receiving' means one lot of letters goes inside another.
'in error' indicates an anagram.
'a'+'prize'='aprize'
'aprize' with letters rearranged gives 'rapezi'.
'ta' going around 'rapezi' is 'TRAPEZIA'.
'giving' acts as a link.
Can you help me to learn more?
(Other definitions for trapezia that I've seen before include "shapes" , "Quadrilaterals with a pair of parallel sides" .)