Friend hiding love shows steel? (5)
I believe the answer is:
alloy
'steel?' is the definition.
(steel is a kind of alloy)
'friend hiding love' is the wordplay.
'friend' becomes 'ally' (I've seen this before**).
'hiding' means one lot of letters goes inside another.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'ally' enclosing 'o' is 'ALLOY'.
'shows' acts as a link.
(Other definitions for alloy that I've seen before include "Devalue" , "temper" , "Eg brass or bronze" , "Metals fused together" , "A mix of two or more metals" .)