Insecure US nurse dropping son off (6)
I believe the answer is:
unsure
'insecure' is the definition.
('unsure' can be similar in meaning to 'insecure')
'us nurse dropping son off' is the wordplay.
'dropping' suggests deleting specific letters.
'son' becomes 's'.
'off' is an anagram indicator.
'us'+'nurse'='usnurse'
'usnurse' with 's' taken away is 'unurse'.
'unurse' anagrammed gives 'UNSURE'.
(Other definitions for unsure that I've seen before include "Lacking confidence" , "Far from certain" , "regarded as somewhat precarious" , "Not certain or decided" , "Not certain, somewhat confused" .)