Two bovines, the second with head slightly back in lake (5)
I believe the answer is:
oxbow
'second with head slightly back in lake' is the definition.
'oxbow' can be an answer for 'lake' (I've seen this before). I'm unsure of the 'second with head slightly back in' bit.
'two bovines' is the wordplay.
'two bovines' can mean two substitutions for 'bovine'.
'bovine' becomes 'ox' (ox is a kind of bovine).
'bovine' becomes 'bow' (I can't justify this - if you can you should believe this answer much more).
'ox'+'bow'='OXBOW'
'the' is the link.
Can you help me to learn more?
(Other definitions for oxbow that I've seen before include "Horseshoe-shaped river bend" , "State of panic or fear" , "Horseshoe-shaped loop of river" , "Horseshoe shaped bend in a river" , "Cut off river loop" .)