Raises the upper end by a pair of lugs (5)
I believe the answer is:
rears
'raises' is the definition.
(rearing is a kind of raising)
'the upper end by a pair of lugs' is the wordplay.
'end' indicates one should take the final letters.
'by' means one lot of letters go next to another.
'a pair of lugs' becomes 'ears' (I can't explain this - if you can you should give a lot more credence to this answer).
The final letter of 'upper' is 'r'.
'r'+'ears'='REARS'
Can you help me to learn more?
(Other definitions for rears that I've seen before include "Raises" , "Sets up" , "Back ends" , "Fosters, brings up" , "bucks" .)