Detain me improperly, making problem for head (8)
I believe the answer is:
dementia
'problem for head' is the definition.
'detain me improperly' is the wordplay.
'improperly' is an anagram indicator (I've seen this in other clues).
'detain'+'me'='detainme'
'detainme' is an anagram of 'DEMENTIA'.
'making' is the link.
(Other definitions for dementia that I've seen before include "Disorder of mental processes caused by brain disease" , "Detain me in distressed state of old age" , "It's caused by brain diseases" , "Neurological condition" , "Severe or persistent mental disorder, often to do with age" .)