Dumpy, small, unfortunate: close to collapse inside (9)
I believe the answer is:
shapeless
'dumpy' is the definition.
(thesaurus)
'small unfortunate close to collapse inside' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'unfortunate' becomes 'hapless' (similar in meaning).
'close to' indicates one should take the final letters (the 'close' to the word).
'inside' means one lot of letters goes inside another.
The last letter of 'collapse' is 'e'.
'hapless' placed around 'e' is 'hapeless'.
's'+'hapeless'='SHAPELESS'
(Other definitions for shapeless that I've seen before include "Amorphous" , "unattractive to look at?" , "Without definite form" , "Lacking definite form" , "unstructured" .)