Thieving, identified lamp first (5,8)
I believe the answer is:
light fingered
'thieving identified lamp first' is the definition.
'light-fingered' can be an answer for 'thieving' (thesaurus). I'm unsure of the 'identified lamp first' bit.
'lamp first' is the wordplay.
'lamp' becomes 'light' (I've seen this before).
'first' becomes 'fingered' (I can't justify this - if you can you should give a lot more credence to this answer).
'light'+'fingered'='LIGHT-FINGERED'
Can you help me to learn more?
(Other definitions for light fingered that I've seen before include "bent on nobbling" , "not heavy-handed?" , "one having criminal tendencies" , "taking on what may be portable" , "Likely to steal" .)