Iron approach needed for cat (6)
I believe the answer is:
feline
'for cat' is the definition.
(I've seen this before)
'iron approach needed' is the wordplay.
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'approach' becomes 'line' (I've seen this in other clues).
'needed' means one lot of letters go next to another.
'fe'+'line'='FELINE'
(Other definitions for feline that I've seen before include "Mog" , "Persian for one" , "Of or like cats" , "Like a leopard, say" , "(Relating to a) cat" .)