Dull little boy's nurse (6)
I believe the answer is:
matron
'nurse' is the definition.
(matron is a kind of nurse)
'dull little boy's' is the wordplay.
'dull' becomes 'mat' ('mat' can be similar in meaning to 'dull').
'little' means to remove the last letter (the word is not quite complete).
'boy's' becomes 'tron' (I can't explain this - if you can you should believe this answer much more).
'mat' with its final letter taken off is 'ma'.
'ma'+'tron'='MATRON'
Can you help me to learn more?
(Other definitions for matron that I've seen before include "Old woman" , "Middle-aged or elderly married woman" , "Head of nursing" , "Medical supervisor" , "Former title of today's Senior Nursing Officer" .)