Tax returns in Yemeni art schools (6)
I believe the answer is:
strain
'tax' is the definition.
(I've seen this before)
'returns in yemeni art schools' is the wordplay.
'returns' is a reversal indicator.
'in' indicates a hidden word.
'niarts' can be found hidden inside 'yemeni art schools'.
'niarts' written backwards gives 'STRAIN'.
(Other definitions for strain that I've seen before include "Family - tension" , "Force - melody" , "Trace" , "Difficulty that causes tension" , "Stretch or exert to the utmost" .)