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 understand how this works, but
'a' is within the answer.
an anagram of 'drug' is 'gurd' which is present in the left over letters.
'boy' could be 'ed' (short for Edward) and 'ed' is located in the answer.
No letters remain.
This explanation may well be incorrect...
'of' is the 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" .)