Cat woman's under pressure to detain soldier (7)
I believe the answer is:
panther
'cat' is the definition.
(I know that Panther is a cat)
'woman's under pressure to detain soldier' is the wordplay.
'woman's' becomes 'her' (belonging to a woman).
'under' means one lot of letters go next to another (below, in a down clue).
'pressure' becomes 'p' (scientific abbreviation).
'to detain' indicates putting letters inside (inserted letters are held or detained).
'soldier' becomes 'ant' (soldier ant is a type of ant).
'her' put after 'p' is 'pher'.
'pher' enclosing 'ant' is 'PANTHER'.
(Other definitions for panther that I've seen before include "See 2" , "Black leopard" , "Bagheera?" , "Then rap the large black cat" , "kind of feline" .)