The doctor should and I would prescribe water for it (7)
I believe the answer is:
drought
'i would prescribe water for it' is the definition.
I can't tell whether this definition defines the answer.
'the doctor should' is the wordplay.
'the doctor' becomes 'Dr' (abbreviation).
'should' becomes 'ought' (synonyms).
'dr'+'ought'='DROUGHT'
'and' is the link.
Can you help me to learn more?
(Other definitions for drought that I've seen before include "Lack of rainfall" , "Period of abnormal dryness" , "Period with little rain" , "Severe water shortage" , "Long dry spell" .)