Stone that's great in construction? (7)
I believe the answer is:
granite
'stone' is the definition.
(granite is a kind of stone)
'great in construction?' is the wordplay.
'construction?' indicates an anagram (answer constructed from certain letters).
'great'+'in'='greatin'
'greatin' with letters rearranged gives 'GRANITE'.
'that's' acts as a link.
(Other definitions for granite that I've seen before include "Constituent in Dartmoor" , "A very hard rock from Tangier" , "Hard stone from Tangier" , "Very hard type of rock" , "Showing great resolution" .)