I am peculiar and altogether indecent (8)
I believe the answer is:
improper
'altogether indecent' is the definition.
'improper' can be an answer for 'indecent' (associated in meaning). I am not sure about the 'altogether' bit.
'i am peculiar' is the wordplay.
'i am' becomes 'I'm' (contraction).
'peculiar' becomes 'proper' (I am not sure about this - if you are sure you should believe this answer much more).
'im'+'proper'='IMPROPER'
'and' is the link.
Can you help me to learn more?
(Other definitions for improper that I've seen before include "Naughty" , "Not decorous or seemly" , "Not in line with accepted standards of morality" , "Unseemly; (fraction) more than one" , "Hardly meet" .)