Sanction tower being rebuilt in lake (8,5)
I believe the answer is:
coniston water
'lake' is the definition.
(I've seen this before)
'sanction tower being rebuilt' is the wordplay.
'being rebuilt' is an anagram indicator.
'sanction'+'tower'='sanctiontower'
'sanctiontower' with letters rearranged gives 'CONISTON WATER'.
'in' acts as a link.
(Other definitions for coniston water that I've seen before include "Cumbrian lake" , "Lake where Donald Campbell died" .)