According to Michael Sandison in an interview with The Guardian, "There's a palindromic structure centred around the track Collapse in the middle."  On Tomorrow's Harvest, there are exactly 8 tracks before Collapse and 8 tracks afterwards.
'Collapse' in this context is most likely a term referring to the sudden failure of a system, organization, business, etc. 
The track is identical in structure when played forward or reversed.
On the vinyl release, Collapse is the final track on Side B. It can be said the abrupt ending of this track is more dramatic than in other media formats, since Palace Posy does not immediately follow, giving Collapse a greater sense of fatalism.