Tongue bends double, finding way in (4)
I believe the answer is:
urdu
'tongue bends' is the definition.
'urdu' can be an answer for 'tongue' (Urdu is a language or tongue). I'm unsure of the 'bends' bit.
'double finding way in' is the wordplay.
'double' shows that letters should be duplicated.
'finding' becomes 'u' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'way' becomes 'rd' (short for road).
'in' is an insertion indicator.
'u' doubled is 'uu'.
'uu' enclosing 'rd' is 'URDU'.
(Other definitions for urdu that I've seen before include "Indic language written in Persian script" , "Language akin to Hindi" , "Sub-continental language" , "Indian language" , "Foreign language" .)