Trendy son sits uneasily to make demands (7)
I believe the answer is:
insists
'demands' is the definition.
(I've seen this before)
'trendy son sits uneasily' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'son' becomes 's' (genealogical abbreviation for son).
'uneasily' indicates anagramming the letters.
'sits' anagrammed gives 'ists'.
'in'+'s'+'ists'='INSISTS'
'to make' acts as a link.
(Other definitions for insists that I've seen before include "Brooks no refusal" , "Maintains persistently" , "Maintains firmly" , "Demands firmly, not accepting refusal" , "Contends" .)