Reg and I'd struggle to the crest of the hill (5)
I believe the answer is:
ridge
'the hill' is the definition.
(I've seen this in another clue)
'reg and i'd struggle' is the wordplay.
'and' says to put letters next to each other.
'struggle' indicates anagramming the letters (letters move around or struggle).
'reg'+'id'='regid'
'regid' anagrammed gives 'RIDGE'.
'to the crest of' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for ridge that I've seen before include "Top line of roof" , "Hog's-back" , "Narrow raised band on a surface" , "Long, narrow hilltop" , "Line where two upward sloping surfaces meet" .)