1 down Sun falling on British couple creates obstacle. two words -T-M---N- BLOCK
11 across Enable pi to be computed but not refined 8 letters ---B----
Thank you...
1d Clue: Untidy reeves mate seen in small city suburbs (7) S ? ? ? F ? Y
8a Clue: Absent minded physicist swaps diamonds for whiskey (7) F ? ? ? W ? Y
5d Clue: Drink over by bar (4) A ? L ?/...