Old but surprisingly keeping most of hair? Hmm! (8)
I believe the answer is:
doubtful
'hmm' is the definition.
I can't tell whether this defines the answer.
'old but surprisingly keeping most of hair?' is the wordplay.
'surprisingly' indicates an anagram (a surprising ordering of the letters).
'keeping' means one lot of letters goes inside another.
'most' means to remove the first letter.
'hair?' becomes 'u' (I can't explain this - if you can you should believe this answer much more).
'old'+'but'='oldbut'
'oldbut' is an anagram of 'doubtl'.
'of' with its initial letter taken away is 'f'.
'f'+'u'='fu'
'doubtl' going around 'fu' is 'DOUBTFUL'.
Can you help me to learn more?
(Other definitions for doubtful that I've seen before include "Unsure" , "Unlikely, questionable" , "Dubious" , "description of Thomas" , "Vacillating" .)