Prompt to redevelop giant site (9)
I believe the answer is:
instigate
'prompt' is the definition.
(I know that prompt can be written as instigate)
'redevelop giant site' is the wordplay.
'redevelop' indicates anagramming the letters (I've seen 'redeveloped' mean this).
'giant'+'site'='giantsite'
'giantsite' anagrammed gives 'INSTIGATE'.
'to' is the link.
(Other definitions for instigate that I've seen before include "Urge and bring about" , "Provoke" , "I taste gin to incite or urge" , "I get saint to urge or incite" , "Set off or stir up" .)