Fifteen across: a bovine beast
That sees a field as one green feast
Three letters: Blank, Oh, Double Yew
And then I’ve solved the final clue

It sees grass as a meal? That’s cheap
Perhaps a goat or maybe sheep
Though they don’t fit inside the gap
I should have had a game of snap

‘A bovine beast’, what does that mean?
These clues use words I’ve never seen
Aha! I think I have it now
Bovine means pig, so that’s a ‘Sow’