Smell that's iffy probed by doctor without interest (7)
I believe the answer is:
humdrum
'without interest' is the definition.
I can't judge whether this defines the answer.
'smell that's iffy probed by doctor' is the wordplay.
'smell' becomes 'hum' (something with a bad smell is 'humming').
'that's iffy' becomes 'um' (I can't explain this - if you can you should give a lot more credence to this answer).
'probed by' is an insertion indicator (probe can mean to poke into something).
'doctor' becomes 'dr' (abbreviation).
'hum'+'um'='humum'
'humum' going around 'dr' is 'HUMDRUM'.
Can you help me to learn more?
(Other definitions for humdrum that I've seen before include "Commonplace, dull" , "Unexciting" , "Dull (of existence)" , "Everyday, boring" , "Dull and uninteresting" .)