A last letter has girl and English boy describing love in summerhouse (6)
I believe the answer is:
gazebo
'summerhouse' is the definition.
(I know that summerhouse can be written as gazebo)
'a last letter has girl and english boy describing love' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
'last' could be 'z' (Last letter alphabet) and 'z' is present in the answer.
'letter' could be 'o' and 'o' is found in the answer.
'girl' could be 'g' and 'g' is located in the answer.
'english' could be 'e' (abbreviation) and 'e' is found within the answer.
'boy' could be 'b' (abbreviation used in schools) and 'b' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
(Other definitions for gazebo that I've seen before include "Small summerhouse or open hut" , "outhouse" , "Summerhouse with views" , "Belvedere" , "Summer house with a wide view" .)