Obvious a mother or father is under pressure (8)
I believe the answer is:
apparent
'obvious' is the definition.
(similar in meaning)
'a mother or father is under pressure' is the wordplay.
'mother or father' becomes 'parent' (I've seen this in another clue).
'is under' means one lot of letters go next to another.
'pressure' becomes 'p' (abbreviation).
'parent' after 'p' is 'pparent'.
'a'+'pparent'='APPARENT'
(Other definitions for apparent that I've seen before include "cut , book written on a page" , "Visible - plain - presumable" , "That may be seen" , "Ostensible, seeming" , "Obvious, evident" .)