Old man crossing the line with nymph in the woods (5)
I believe the answer is:
dryad
'nymph in the woods' is the definition.
'dryad' can be an answer for 'nymph' (dryad is a kind of nymph). I'm not sure about the 'in the woods' bit.
'old man crossing the line' is the wordplay.
'old man' becomes 'dad' (synonyms).
'crossing' indicates putting letters inside.
'the line' becomes 'ry' (abbreviation for railway).
'dad' going around 'ry' is 'DRYAD'.
'with' is the link.
Can you help me to learn more?
(Other definitions for dryad that I've seen before include "one stuck in a tree" , "Nymph of the woods" , "Beautiful young woman" , "Spirit in the wood" , "butterfly" .)