Just the job for one adult in Delaware (5)
I believe the answer is:
ideal
'just the job' is the definition.
(I've seen this before)
'one adult in delaware' is the wordplay.
'one' becomes 'i' (Roman numeral).
'adult in delaware' becomes 'deal' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'i'+'deal'='IDEAL'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for ideal that I've seen before include "Very eager (to see)" , "Model of excellence (5)." , "Cutting/stabbing weapons" , "Optimal" , "principle to be aimed at" .)