Claim source of emotional stress is supporting Spurs regularly (10)
I believe the answer is:
pretension
'claim' is the definition.
(I've seen this before)
'source of emotional stress is supporting spurs regularly' is the wordplay.
'source of' indicates taking the first letters.
'stress' becomes 'tension' ('tension' can be a synonym of 'stress'**).
'is supporting' says to put letters next to each other (in a down clue, some letters go below others).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The initial letter of 'emotional' is 'e'.
The alternating letters of 'spurs' are 'pr'.
'e'+'tension'='etension'
'etension' after 'pr' is 'PRETENSION'.
(Other definitions for pretension that I've seen before include "A claim or aspiration (to something)" , "inappropriate style" , "false claim" , "Show" , "Spurious claim, aspiration" .)