Get anxious about lifting top (7)
I believe the answer is:
sweater
'top' is the definition.
(type of top or jumper)
'get anxious about lifting' is the wordplay.
'get anxious' becomes 'sweat' (sweat can mean to become worried or anxious).
'about' becomes 're' ('re' means regarding or about).
'lifting' shows that the letters should be reversed in order.
're' back-to-front is 'er'.
'sweat'+'er'='SWEATER'
(Other definitions for sweater that I've seen before include "Jumper (7)" , "Guernsey" , "person in a sauna?" , "Top" , "Jumper or jersey" .)