I am playing with ants’ legs (7)
I believe the answer is:
stamina
'legs' is the definition.
(I've seen this before)
'i am playing with ants'' is the wordplay.
'playing with' is an anagram indicator.
'i'+'am'='iam'
'iam' with its letters anagrammed with 'ants' can make 'STAMINA'.
(Other definitions for stamina that I've seen before include "grit" , "Resilience" , "Parts of flowers" , "toughness in > male parts" , "Ability for sustained effort" .)