Girl seen on the moors (7)
I believe the answer is:
heather
'girl' is the definition.
'on the moors' is the wordplay.
'on' indicates putting letters inside (as in clothing 'on' a person).
'moors' becomes 'hear' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the' inserted within 'hear' is 'HEATHER'.
'seen' acts as a link.
Can you help me to learn more?
(Other definitions for heather that I've seen before include "Moorland flower" , "Small purple evergreen plant growing on hills" , "Another term for ling" , "Moorland flora" , "Evergreen shrub" .)