Guru thanked participants for compassion (4)
I believe the answer is:
ruth
'for compassion' is the definition.
(as opposed to ruthlessness)
'guru thanked participants' is the wordplay.
'participants' indicates a hidden word (some letters 'participating' in the clue).
'RUTH' is hidden within 'guru thanked'.
(Other definitions for ruth that I've seen before include "Babe -, US baseball player" , "Lady" , "Damsel" , "condolences?" , "Remorse in Book of Bible?" .)