First off, shortage of dry land (5)
I believe the answer is:
earth
'dry land' is the definition.
(synonyms)
'first off shortage' is the wordplay.
'first off' means to remove the first letter.
'shortage' becomes 'dearth' (synonyms).
'dearth' with its initial letter taken off is 'EARTH'.
'of' acts as a link.
(Other definitions for earth that I've seen before include "It is necessary to clear" , "Huge cost" , "Human world" , "The 3rd planet from the sun" , "underground shelter" .)