A part of dress that's said to require attention (4)
I believe the answer is:
ahem
'that's said to require attention' is the definition.
(cough used to attract attention)
'a part of dress' is the wordplay.
'part of dress' becomes 'hem' ().
'a'+'hem'='AHEM'
(Other definitions for ahem that I've seen before include "Half-cough to draw attention" , "Utterance of mild disapproval" , "Attention-getter" , "Expression of disapproval" , "Polite noise to draw attention" .)