Area clear and dry (4)
I believe the answer is:
arid
'dry' is the definition.
(similar in meaning)
'area clear' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'clear' becomes 'rid' (synonyms).
'a'+'rid'='ARID'
'and' acts as a link.
(Other definitions for arid that I've seen before include "Excessively dry" , "Dry and parched, as with regions" , "Dry raid" , "Drought-hit" , "(Of an area) very dry" .)