Grab two animals from below (6)
I believe the answer is:
tackle
'grab' is the definition.
(I've seen this before)
'two animals from below' is the wordplay.
'two animals' means two replacements for 'animal'.
'animal' becomes 'elk' (I have seen 'American animal ' mean 'elk' so perhaps 'animal' could also mean 'elk').
'animal' becomes 'cat' (cats are animals).
'from below' says the letters should be written backwards (in a down clue, letters go up).
'elk'+'cat'='elkcat'
'elkcat' in reverse letter order is 'TACKLE'.
(Other definitions for tackle that I've seen before include "things" , "Grab" , "Have a go at (problem)" , "Equipment; intercept" , "Robust feature of football" .)