take it off?
I'm not familiar with defenders but can you not just remove the grill and if needs be nudge the rad back a smidge?
Heres a tip - you'd always leave the engine running anyway when using a leccy winch. In truth winches draw more than a battery can ever give anyway.
Plus, winch technique should be to 'drive assist'. You'd always use a winch to assist in recovery whilst attempting to drive.
The winch on its own, well, if you do the mathematics on current draw you'll find it isn't a viable option to rely on, on its own.
Just fit the fecker! you can always rewire it later if the need or desire arises.