Cautious of administering a drug as a boy (7)
I believe the answer is:
guarded
'cautious' is the definition.
(similar in meaning)
'administering a drug as a boy' is the wordplay.
I cannot quite see how this works, but
'a' is within the answer.
an anagram of 'drug' is 'gurd' which is located in the remaining letters.
'boy' could be 'ed' (short for Edward) and 'ed' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for guarded that I've seen before include "Reticent" , "Cagey or protected" , "Cautious; watched over" , "Kept watch over" , "with escort" .)