Pick up skinny guards close to border (5)
I believe the answer is:
learn
'pick up' is the definition.
(synonyms)
'skinny guards close to border' is the wordplay.
'skinny' becomes 'lean' (similar in meaning).
'guards' is an insertion indicator (inserted letters are guarded).
'close to' indicates one should take the final letters (the close/ending of).
The last letter of 'border' is 'r'.
'lean' going around 'r' is 'LEARN'.
(Other definitions for learn that I've seen before include "Con" , "Comprehend" , "Absorb as knowledge, from book or experience" , "Succeed in school" , "Commit to memory" .)