Boarding schoolmate's pal located around ruin (8)
I believe the answer is:
collapse
'ruin' is the definition.
(I've seen this before)
'boarding schoolmate's pal located around' is the wordplay.
'boarding' indicates the answer is hidden within the clue (the answer is 'on board' the clue).
'around' says the letters should be written in reverse.
'espalloc' can be found hidden inside 'schoolmates pal located'.
'espalloc' back-to-front is 'COLLAPSE'.
(Other definitions for collapse that I've seen before include "Go to ruin" , "Break down - fall" , "Fall down as from weakness" , "Fall down suddenly like escallop" , "Slump" .)